Senator Richard Blumenthal of Connecticut referred to the Boeing 737 Max as 'flying coffins.'
The development has come just two weeks after the company acknowledged that it had to correct defects in its 737 MAX flight stimulator, which are used to train pilots.
Boeing is increasingly optimistic about gradually making a mid-market plane to fill gaps in its lineup
Boeing voiced more optimism on Tuesday about going ahead with a new aircraft to fill a gap in its product line, but said the time frame for producing such a plane remained years away.
According to Boeing's estimates, Air India hiked capacity by 7 percent, Jet Airways by 13 percent, IndiGo by 23 percent this July versus July 2014.