British Airways chief executive Willie Walsh offered his apologies to passengers affected by the cancellations and warned that "some disruption" is expected to continue through Saturday, The Times of London reported Friday.
Walsh said the airline, which is the sole inhabitant of Terminal 5, expects to operate about 80 percent of its scheduled Friday flights.
Fifty-nine flights were canceled on the terminal's first day of operation Thursday, and 75 flights were canceled before noon Friday, affecting an estimated 14,000 passengers, The Telegraph reported.
Walsh put the blame for the terminal's troubles on both British Airways and BAA, the airport operator.
"We clearly got things wrong," he said.
The executive said additional employees have been called into the airport to help ease long lines that some passengers said led them to miss their flights.