Top U.S. airline carriers United Airlines (UAL  ) and American Airlines (AAL  ) this week boosted outlooks for post-summer travel bookings, signalling that there is no slowdown in consumer demand.

Shares of United and American soared 11% and 9%, respectively, for the week as investors were encouraged that the airline industry is making bigger strides towards pandemic recovery. The positive outlooks also carried over to other airline stocks, with Southwest Airlines (LUV  ), Delta Air Lines (DAL  ) and Alaska Air Group (ALK  ) each rising over 4% for the week.

Airline-focused exchange-traded fund (ETF) U.S. Global Jets ETF (JETS  ) also climbed over 3% over the past week.

Domestic carriers saw a surge in passengers over the Labor Day weekend, with the U.S. Transportation Security Administration (TSA) screening nearly 8.76 million people from Friday through Monday. That total surpassed pre-pandemic levels for the same weekend in 2019, where the TSA screened 8.6 million travellers.

This was the first time holiday travel demand topped 2019 levels since the start of the coronavirus pandemic, marking a milestone in U.S. airlines' recovery. Throughout the pandemic, U.S. airlines faces numerous challenges including staff shortages and soaring fuel costs, which have affected their recovery.

Travel demand typically cools down after Labor Day, which is unofficially considered the end of the summer season. However, United Airlines currently sees no slowdown in ticket sales between August and September.

"We're seeing a really strong September," said Patrick Quayle, senior vice president of global network planning and alliances at United during a Cowen industry conference on Wednesday. "It does not appear that summer has come to an end. It's that strong."

United also raised its third-quarter sales forecast amid strong reported demand. The Chicago-based carrier now expects total operating revenue in the current quarter to be up 12% from the same period in 2019, up from a prior forecast of 11%.

American Airlines Chief Executive Officer Robert Isom said at the same conference that leisure bookings are remaining "strong" heading into September, and the airline continues to see "revenue and expense and margin tracking as we expected".