WASHINGTON (REUTERS) - US summer air travel will hit a new record this year despite the grounding of Boeing's 737 Max aircraft after two fatal crashes, a group representing major airlines said on Tuesday (May 21).

Airlines for America, the trade group representing major US carriers, said it expects 257.4 million passengers to travel on US airlines between June 1 and Aug 31, up 3.4 per cent from last summer's record 248.8 million passengers.

Airlines are adding 111,000 seats daily to accommodate the extra 93,000 passengers expected per day, the group said, in what it forecast will be the 10th consecutive summer of increases in the number of US airline passengers.

Southwest Airlines Co and American Airlines Group Inc have cancelled flights because of the grounding of the 737 Max into August, while United Airlines has cancelled flights into early July.

Southwest has cancelled 160 daily flights through Aug 5. It launched service to Hawaii earlier this year but has had to defer flying there from San Diego and Sacramento because of the Max groundings.

American has cancelled nearly 115 flights daily until Aug 19, accounting for 2 per cent of its summer flight capacity.

The US Transportation Department said that July 2018 was the all-time busiest air travel month, with 75.8 million passengers.

The Federal Aviation Administration is meeting with aviation regulators from around the world in Texas on Thursday to update them on the various reviews of the 737 MAx.

Boeing has not yet formally submitted its software upgrade and training revisions to the FAA for approval or completed a certification flight.