United Airlines Grounds 96 Boeing 757s CheapOair Staff February 16, 2011 general United Airlines had to ground nearly 100 Boeing 757 airliners Tuesday after it was discovered the carrier did not follow some safety checks related to important equipment upgrades that federal aviation regulators require. United does not foresee any cancelations and minor delays Wednesday after it had to park 96 planes for the unscheduled maintenance. A spokesman for the airline said more than a dozen flights were axed Tuesday to the procedures taking place. The check ups took approximately 60-90 minutes per plane according to the Chicago based carrier. The Federal Aviation Administration commented on the situation by saying United was compliant with a 2004 airworthiness directive issued to all airlines.