There's just something about flying solo that gives one the sense of being anonymous — nobody knows your name, where you're from, or where you're going. You could even make up a new identity to entertain your neighbors and they would have no way of finding out who you really are. But rest assured, your flight attendant does.

In the back, the flight crew probably has a photo of your face on their sophisticated tablets, which could tell them a slew of other personal information, including your birthday, your occupation, your favorite beverage, and how your last five flights have gone. They even have notes from the ground crew that could tell them whether you're in a bad mood.

The airline knows even more, potentially including credit card information, which hotel you'll be staying in, home address, and more. Carriers have more information on their passengers than ever before, both to improve customer service and to decrease the risk of terrorism, but many passengers say it's getting to be too invasive. Here are 20 things you don't even realize your airline knows about you.

20 Birthdays

These days, you shouldn't be surprised if you happen to be flying on your birthday and the flight attendant gifts you a card signed by the crew. Most attendants are not only aware that it's your birthday but also what age you're turning, too. For instance, The Sun says that JetBlue attendants are equipped with a tablet showing the layout of the plane and details of each passenger. In the case of a birthday, the tablet will show a cake icon over the person's seat. Wall Street Journal beckons the question: "is that cute or creepy?"

19 Where they're from

They also know your home address, and not from your luggage tag (which, by the way, the Daily Express says never to do). They received this information, of course, when you booked the flight online. And what do they intend to do with it? Certainly not send you a bouquet, unfortunately. A 2015 Los Angeles Times article says that a system called Resolution 787 "allows airlines to collect data from passengers and exploit the information for marketing purposes." While airlines have denied that they sell this information to third parties, they admit that they do, indeed, "share" it with their partners, the article says.

18 And where they're going

What's even creepier? Airlines not only know where its flyers are from but also where they're going. One could argue that this is necessary and beneficial information for flight attendants to have. After all, they can use it to help you catch your connecting flight in time. United Airlines attendants use an app that shows them details about each customer, including whether they're traveling with a pet or have lap children, the Wall Street Journal article says. This app also shows connecting flights for passengers in color codes: green for good, yellow for ones that could be in trouble, and red for tight connections.

17 Which hotel they're staying in

If you think that's a bit stalkerish, things are about to get even creepier. If you've booked a vacation bundle — say, a hotel and a rental car with your flight — then your airline likely knows precisely the hotel in which you'll be staying when you arrive. In the European Union, airlines store their passengers' personal information and travel details for five years, including hotel bookings, The Independent says. You can just assume that anything you type into the website upon booking will be added to your virtual travel file for a while.

16 Their last five flights and how they went

Airlines know where you're from, where you're going, and where you've been. If you're a United Frequent Flier, the flight attendants can see — on this new app — the details of your past five flights. They are highlighted in green if the flight went well and red if something bad happened, like a delay or lost luggage, Wall Street Journal says. According to a flight attendant and contributor to The Points Guy, Carrie A. Trey, the tablets that American Airlines attendants are using these days include notes from other attendants on previous flights, such as, the blog says, "14A was mistreated by the last crew and the flight was delayed too, so please make sure they get the VIP experience."

15 Beverage purchases

These notes, however, will also advise the flight crew of whether you've had one too many toddies on your connecting flight or at the airport bar, Carrie A. Trey says. If you've had too much, they can — like any good bartender — refuse to serve you more. The Wall Street Journal says that one aim of the JetBlue tablet system is to track its passengers' purchases. They want to know how you take your coffee, or if you order the same beverage each time you fly, so they can offer you the usual.

14 Special diets

They know what you drink and they know what you eat, too. Of course they do: they're your in-flight waiters after all, and they must know what to feed you. Flight attendants know who's vegan, kosher, and low sodium. They know if you're fussy about food and if you're a procrastinator, too. If you've made a special meal request within 24 hours of the flight, you could be flagged on their app or tablet with the code "LTRQ," Carrie A. Trey tells The Points Guy, which stands for "late request." Shame on you!

13 Who has allergies

This means they're aware of any allergies you might have, too, whether or not they pertain to food. Your virtual profile will show whether you are lactose intolerant, coeliac, or have a peanut allergy (indicated by the code "PNUT," Carrie A. Trey says). In the case of serious allergies, some airlines will have a flight attendant request that nobody on the plane eat that food during the flight, The Guardian says. According to the New York Times, JetBlue will create a "buffer zone" for those who are allergic to peanuts, while Southwest Airlines and Delta won't serve peanuts on that particular flight at all.

12 How many seats they really paid for

There's perhaps no greater feeling of relief than when you strap into a long-haul international flight and, after nervously waiting to discover who your neighbor will be for the next dozen-or-so hours, realizing that you don't have one! You'll do anything to protect the empty seat beside you — for that extra bit of room to stretch out on — so when the flight attendant tries to seat someone there during the flight, you tell them you've paid for the extra seat. But they know you're lying. They can see it on their nifty iPads, marked "EXST" for "empty seat." Carrie A. Trey says she gets this line all the time but only once or twice per year is it true.

11 And whether they actually paid for that upgrade

Similarly, they also know whether you've paid for extra legroom or your business class seat, or you're just a cheap skate with a bit of luck. You might think that getting upgraded for free means you'll be treated like a king, and you might be, but you probably won't be treated quite as royally as the folks who actually paid for those seats, the Wall Street Journal says. Travelling on a restricted economy ticket? They know that, too, although they're not supposed to let it affect how they serve you.

10 Economic status

Flight attendants know if you're cheap, yes, and — hopefully — don't use it against you; however, studies show that the airlines do. When you go online to book a flight, airlines gather information stored in cookies and consumer accounts, The Telegraph says, and this information includes your salary. Airlines are starting to use this information to determine a personalized cost of the flight in real time, the article says, taking into consideration age, salary, and loyalty, among other things. It's called fare discrimination. Who knew that the price of flights could be unique to you?

9 Contact information

In the air travel industry, airlines keep a record of their passengers in what they call a PNR, a "passenger name record." It could include the passenger's itinerary, fare details, how the passenger paid, any special services required, age, and sometimes gender, too. This is a government-required personal file kept in a computer reservation system. Your PNR, for example, would have all your past travel details from every airline, including your personal contact information, such as email and phone number, as well as a redress number if you've ever given one.

8 Orientation & Affiliations

These are things your airline has access to but allegedly doesn't use. According to Forbes, the information airlines have on its passengers is being supplemented by data brokers who could know whether they're gay, straight, a democrat, or a republican. But while they are able to use this information to leverage targeted travel market campaigns, United Airlines' Thomas O'Toole told Forbes that United doesn't use such personal, intimate details. "We are interested in characteristics related to flight behavior," he said in the article.

7 Their computer IP addresses

In the same way that your contact information and travel itinerary are logged in your passenger name record, all as a result of booking your flight online, the data that airlines collect from you could also include your computer's IP address, according to The Independent. This computer IP address is unique to the network on which you booked your ticket online, meaning: if airlines are collecting this data, they can see exactly where you purchased your ticket. If you've booked the flight from home, you wouldn't want your home IP address floating around in cyberspace because it could make you vulnerable to potential hackers.

6 Why they're flying

Flight attendant Carrie A. Trey told The Points Guy that she uses a document that identifies various things about each passenger with codes. For instance, there's a code for folks traveling in groups — indicating, perhaps, a holiday — and also one to indicate that a passenger is a deportee. Again, airlines say this information isn't meant to dictate how the attendants treat passengers. Either way, the cabin crew knows whether you're traveling on a high-profile business trip or a bachelorette party, despite whether you wear a suit or a bikini on board.

5 Their occupation

Reader's Digest says there are more than 300 of these acronym codes — a kind of secret language that flight attendants have to memorize — and a number of them pertain to the passenger's occupation. There are special codes for people who are part of a ship's crew, law enforcement officers, and diplomats traveling with official documents, Carrie A. Trey says. There's also a code for veterans, which Reader's Digest says aims to inform crew members so they can thank them for their service. Of course, many of us have less high-profile occupations, and there isn't a code for "Starbucks barista," so we're safe.

4 Whether they have a bad attitude

The virtual systems that cabin crews are using these days often have notes sections where airline employees on the ground — that is, working at the ticket counters and information desks — can write in a little heads up to the cabin crew in real time if a passenger has a flat out bad attitude. According to the Wall Street Journal, carriers say that they don't flag bad behavior or "problem travelers" on these systems; however, Carrie A. Trey told The Points Guy they might. They could make a note saying "3B missed their last flight because TSA held them up and he's really angry," Trey used as an example.

3 How many miles they've flown

On United Airlines' new color-coded map, The Wall Street Journal reported, the color can depict frequent fliers and just how many million miles they've bagged with the airline. The article uses the example of seat 7C marked on the map with a "3M," meaning the passenger has flown 3 million miles. Carrie A. Trey told The Points Guy that this isn't necessarily a new feature; Emirates has been able to see this information on their laptops for about a decade now. Flight attendants use the feature to congratulate their loyal customers on such milestones.

2 Credit card details

Just like your airline has your contact information and IP address, it can store the details of the credit card you paid with, too, according to The Independent. In 2015, when the European Union started requiring airlines to log personal information — in the passenger name record — from each person who came in and out of the EU, it resulted in "the mass harvesting of innocent people's data," the article says. Of course, this is governmental law specifically put in place to cut down on terrorism, so it isn't likely that these details could be used by criminals but having your credit card details in someone else's hands is never comfortable, nonetheless.

1 Whether they need a wheelchair

This might also seem like essential information for flight attendants dealing with passengers with special needs. On United's high-tech system, the virtual seat indicates whether the passenger needs a wheelchair to disembark, The Sun says. Flight attendant and The Points Guy contributor Carrie A. Trey says that having this information helps her to better accommodate passengers with disabilities. These codes go as far as letting the cabin crew know whether passengers are bringing their own wheelchair or borrowing one from the airport, or whether they're hearing or visually impaired.