BOSTON—U.S. airlines are looking at the upcoming holiday season and the reopening of vital trans-Atlantic routes to recover the momentum lost in the last quarter following a resurgence in COVID-19 cases. After a strong summer travel season, air carriers had to temper their outlook last month for the quarter through September as the fast-spreading Delta variant of the coronavirus slowed down new bookings and drove up cancellations. A month on, dipping COVID-19 cases have raised industry hopes that passengers would be more confident to fly again. Financial services firm Raymond James conducted an analysis of the Transportation Security Administration’s 7-day average passenger screening data, which showed that while the travel demand still lags the peak in late July, it has improved from the lows in mid-September. “Cancellations have abated, bookings are recovering,” Hawaiian Airlines and Hawaiian Holdings Chief Executive Peter Ingram told Reuters in an interview. “As we get to …