A leading online travel agent has added filters to let users exclude flights that use Boeing’s troubled 737 Max planes, after a piece of fuselage falling off an Alaska Airlines flight led to a surge of user interest in avoiding the airliners. Kayak first introduced an aircraft filter in March 2019, to add and exclude specific models of plane, but the company says it saw little use compared with the more prominent filters of the number of stops or airports. Following the Alaska Airlines incident, it says there was a 15-fold increase in use of the original filter, prompting it to rework the setting, making it more prominent on the search page and adding the ability to distinguish between 737 Max 8 and Max 9 planes, since only the latter has been grounded by America’s Federal Aviation Administration. “Whether you’re searching by cabin class, flight quality or aircraft type, Kayak’s filters aim to provide travellers with all the information they need to make smart decisions and travel with confidence,” a company spokesperson said. The surge of interest in the new feature demonstrates the unusual extent to which typical travellers are actively avoiding the 737 Max planes. Such filters are more commonly used by regular travellers with esoteric preferences around particular seat locations on various planes, rather than a broad-brush fear of an entire family of jets. On Sunday, the FAA expanded its scrutiny of Boeing jets to another, older model of 737, the 737-900ER, which it says uses a similar door design. “The safety of the flying public, not speed, will determine the timeline for returning these aircraft to service,” it said. In response, United Airlines, which has 79 737 Max 9s and a further 136 737-900ERs in its fleet, issued a profit warning. The airline has more of the affected planes than any other, and it forecasts that it will not be able to fly them again until at least February. In its annual earning report on Tuesday, United reported flat pre-tax profits of $3.4bn for 2023, but said it expected to lose money in the coming quarter.