Can you fly an airliner without an ATPL?
You don't have to be an ATP to fly an airliner. In fact, you can fly an airliner as a private pilot. John Travolta is the best example I can think of... He has a house right by a private airport and flies his own personal Boeing 707 (with Qantas livery) and another jet aircraft (Gulfstream I think). With any large aircraft like this over 12500 lbs or with turbojet engine(s), a pilot does need a type specific rating to fly such an aircraft as well as needing to be "current" in that type, but may do so as long as current at any certificate "level" of private pilot or above. However, to fly an airliner as a scheduled air carrier pilot, then yes, an ATP is required as this type of flight would not fall under part 91 or part 135 of the FARs, but instead part 121 which requires that all pilots have ATP certificates.