The first Max aircraft entered commercial service in 2017, but the line was grounded in March 2019 for more than 18 months following two fatal crashes, which claimed 346 lives.

The issue was traced to a faulty flight control system, which was found to have sent the two Max 8 flights into an irretrievable nosedive. The issue has now been resolved.

’Despite its problems, Boeing’s 737 Max is here to stay’

Several airlines have since grounded a separate Max model, the Max 9, after a door plug blew out on an Alaska Airlines service earlier this month leaving a gaping hole in the fuselage.

Kayak introduced an aircraft filter in March 2019, but it was only after the Alaska Airlines incident that it saw a dramatic 15-fold uptick in use of the original filter.

A spokesperson for the OTA this week confirmed Kayak has now tweaked the feature to make it more prominent and to distinguish between Boeing’s 737 Max 8 and Max 9 models.

Stan Deal, president and chief executive of Boeing Commercial Airplanes, earlier this month said Boeing was "taking immediate actions to bolster quality assurance and controls" across its factories.

Dozens of 737 Max 9 aircraft have already been grounded as a result of the Alaskan Airlines incident, with the US Federal Aviation Administration looking into the issue.