Frequent travelers are familiar with the big carriers of the world. That list includes United, British Airways, Delta, and American Airlines. But did you know that there are hundreds of commercial airlines currently in operation? Some of them cater to a very specific clientele or only fly particular routes a few months out of the year. If you are looking to book your next flight, they may be worth checking out. Here are five airlines you've probably never heard of until now.

Eurowings

Have a sense of adventure? Then book your next flight on Eurowings. Owned by Lufthansa, the airline offers a unique way of booking your next vacation. They call it a "blind booking." You start by choosing your preferred departure airport and selecting the category of vacation you want to go on. You can choose from categories such as shopping, beach, or nature. Then you pick your dates and book your discounted ticket. Once you've done that, you'll find out where you are actually going.

Of course, you can book tickets the old fashioned way with the airline, too. The budget airline offers three ticket pricing levels, from the no-luggage-no-frills cheap seats to business class with all the extras. You'll want to book your flight soon, though. AIN Online reports the airline experienced an operating loss of $292 million in the first quarter of 2019.

Janet Airlines

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Unless you have some impressive credentials or enough security clearance to get you into the Pentagon, there is a good chance you won't ever be flying this airline. Janet Airlines is the name given to a fleet operated by the U.S. government, according to Business Insider. The airline operates primarily out of Las Vegas, where it shuttles workers back and forth to the Area 51 military base. You can imagine this sparks the imagination of conspiracy theorists out there. But the airline services other military bases and government operations as well, with all the planes owned by the U.S. Air Force. Even the flight attendants who work for the airline must have top-secret military clearance.

Where did the name Janet come from? It may be an acronym for "Joint Area Network for Employee Transportation." But the joke in the aviation industry is that it stands for "Just Another Non-Existent Terminal." Either way, you won't find flights listed for this airline online.

Air Koryo

This is the state-owned airline of North Korea, and it's long been considered to be the worst airline in the world. According to the Telegraph, the airline was the only 1-star rated carrier on the ranking website Skytrax for years. North Korean leader Kim Jong Un is eager to reform the image of the airline, and the efforts have had some success. One of the passengers' biggest concerns is the age of the fleet. The majority of Air Koryo's airplanes are at least 20 years old. An infusion of government funds allowed the fleet to bring in some updated airplanes. The in-flight entertainment leaves something to be desired, too. Bloomberg reports it's all propaganda videos touting the virtues of the country's Supreme Leader.

You might want to pack your own lunch for the flight. The meals onboard the flight consist of something flyers have dubbed the "Mystery Burger." No one knows what it's made of, and officials declined to comment when contacted by reporters.

This might be an airline worth skipping. However, if you are curious about the most isolated country in the world, booking a flight on the North Korean airline will give you a glimpse behind the curtain.

La Compagnie

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If you are looking for a bit of luxury during your time in the air, French airline La Compagnie has it covered. They offer so many amenities you may find yourself wishing the flight was longer. They dub themselves the "all-business class boutique airline," offering up to three nonstop flights per day from Paris to New York. The company packs the planes for comfort too, having only about 75 seats to a flight. Those seats recline to 175 degrees and have built-in massage features, reading lamps, and outlets. Each passenger receives their own tablet for the flight. The tablets have movies, television shows, and even books and newspapers.

You won't have to go hungry on these flights. World-famous chef Christophe Langree developed the onboard menu. It includes a four-course meal for each passenger. You'll dine on a starter, main, cheese plate, and dessert. If you are feeling peckish before landing, don't worry. The airline will provide you with a snack box before the wheels touch down, with both sweet and savory treats.

Kulula Airlines

If you plan on traveling to South Africa sometime, this is an airline worth knowing. Kulula Airlines is a low-cost airline operating out of Johannesburg. And while they offer plenty of great deals on flights around the lower half of the African continent, what makes them famous is the company's sense of humor. That's easy to see from the messages that cover the airline's fleet of bright green planes. Arrows point out the pilot and co-pilot, where the front door is, and even which way is up (maybe not the most comforting sign for nervous flyers). The airline issued a press release about their "Flying 101" planes, commenting on their surprise that they received international attention for their whimsy.

Their sense of humor doesn't stop at their airplanes. According to South Africa Travel Online, the airline issues an annual April Fools prank. In 2014, it announced it would allow passengers to cook either meat or vegetables on its in-flight grills. Flight attendants also perform humorous safety briefings before takeoff, in an attempt to make passengers feel more relaxed. If having a laugh makes you feel more relaxed before your flight, then this is the airline for you.