Documents released by a Senate committee Tuesday are questioning safety on Southwest flights.

Whistleblowers within the Federal Aviation Administration (FAA) want to know whether the airline improperly flew jets without full knowledge of their safety history.

The documents show Southwest bought nearly 90 used jets from foreign airlines, and the FAA gave them the green light to fly. 

A more detailed audit reveals the planes actually need hundreds of major repairs. The Senate committee says thousands of flights were flown like this.

The airline insists the planes are safe, and that the problem was "miscommunication."