US political leaders as well as a union representing tens of thousands of flight attendants are calling on the Federal Aviation Administration to ground a new version of the Boeing 737 jetliner that has come under scrutiny after two crashes in five months that killed everyone on board each time.

A growing list of countries, including Britain, France, Australia, and China, as well as individual airlines across the world have already temporarily grounded their 737 Max 8s.

On Tuesday morning, Democratic US Senator Elizabeth Warren of Massachusetts, a 2020 presidential candidate, called on the FAA to “immediately ground this plane in the United States until its safety can be assured.”


“Today, immediately, the FAA needs to get these planes out of the sky,” Warren said in a statement.

US Senator Mitt Romney, a Republican from Utah and former governor of Massachusetts, tweeted, “Out of an abundance of caution for the flying public, the @FAANews should ground the 737 MAX 8 until we investigate the causes of recent crashes and ensure the plane’s airworthiness.”

Republican US Senator Ted Cruz of Texas as well as Democratic senators Edward J. Markey of Massachusetts, Richard Blumenthal of Connecticut, and Dianne Feinstein of California also called for the planes to be grounded.

President Trump weighed in via Twitter on Tuesday, saying airplanes “are becoming far too complex to fly.”

And the Association of Flight Attendants, a union representing 50,000 flight attendants at 20 different airlines, called for the Max 8s to be grounded.

On Sunday, a 737 Max 8 crashed six minutes after taking off in clear weather from Ethiopia’s capital en route to Nairobi, killing 157 people. The cause had not been determined by Tuesday morning and aviation experts say it could take months to get answers.


In late October, a 737 Max 8 also crashed in Indonesian seas, killing 189 people. A preliminary report on that disaster indicated that pilots struggled to maintain control following an equipment malfunction.

Safety experts cautioned against drawing too many comparisons between the two crashes until more is known.

Still, the carrier involved in Sunday’s crash, Ethiopian Airlines, decided Monday to ground all its 737 Max 8 planes until further notice.

Airlines in Germany, Ireland, Austria, Indonesia, and Oman, as well as Aeromexico, Brazil’s Gol Airlines, India’s Jet Airways, South Korea’s Eastar Jet, Turkish Airlines, and others have temporarily grounded their 737 Max 8s. Malaysia, Australia, and Singapore suspended all flights of 737 Max planes into or out of their countries.

The US-based Boeing, however, has said it has no reason to pull the popular aircraft from the skies, and it does not intend to issue new recommendations about the aircraft to customers.

The FAA on Monday issued a noticed saying it considers the 737 Max fleet to remain airworthy. The federal agency said it expects Boeing will soon complete improvements to an automated antistall system suspected of contributing to the October crash, and update training requirements and related flight crew manuals.

Officials in Canada have also said they don’t plan to ground the planes.

Materials from wire services were used in this report. Matt Rocheleau can be reached at matthew.rocheleau@globe.com. Follow him on Twitter @mrochele