Chicago-area passengers headed to London for the second time in 24 hours Friday after mechanical issues forced their aircraft back to O'Hare Thursday evening.
United Airlines Flight 928 left O'Hare International Airport at 6:10 p.m. Thursday but returned abruptly after the pilot reported problems with the ailerons, flaps at the back edge of the wings that help control sideways movement, Federal Aviation Administration officials said.
The Boeing 767 aircraft turned back and landed safely at O'Hare at 9:49 p.m., United spokeswoman Jennifer Bohm said.
The airline couldn't give details on what caused the problem. "We are doing a complete review of the return and cannot provide further information at this time," Bohm said in an email.
"After returning to the airport, the flight was canceled, and we have reaccommodated all customers on flights to London today," she added.
Emergency crews, including the Chicago Fire Department, were called out to the airport to stand by in case of trouble.
The Boeing 767 was bound for Heathrow International Airport.