Airline ratings: The world's best (and worst) carriers

(FOX News) - The results are in and … no U.S. airline reached the top 20 in a new ranking of the world's best carriers.

American Airlines was the highest-ranked U.S.-based carrier on flight compensation company AirHelp's 2018 list of the best and worst airlines, at No. 23. United was the next highest at No. 37, while Delta rounded out the nation's "Big Three" airlines, claiming the 47th spot.

Both United and Delta have found themselves in the midst of public relations nightmares over the past several months, with snafus resulting in the deaths of animals both in the aircraft's cabin and in its cargo hold. Last week, a dog died during a trip from Phoenix to Newark, New Jersey. United had a string of incidents in March - including the death of a puppy - after a flight attendant forced the customer to put the dog in an overhead compartment. The airline had the worst rate of pet deaths in 2017 among U.S. airlines.

Qatar Airways claimed the top spot on AirHelp's list, dethroning Singapore Airlines, after improving their on-time performance and claim processing. The Middle Eastern air carrier was named "Airline of the Year" in 2017 by SkyTrax, an air carrier ratings organization.