Lawmakers on Capitol Hill are calling for all Boeing 737 Max 8 aircraft to be grounded after a crash in Ethiopia's capital killed all 157 on board. Sens. Richard Blumenthal of Connecticut, Dianne Feinstein of California and Mitt Romney of Utah called on the Federal Aviation Administration to ground the jets in the U.S. until an investigation into the cause of the crash is complete.

"Until the cause of the crash is known and it's clear that similar risks aren't present in the domestic fleet, I believe all Boeing 737 Max 8 series aircraft operating in the United States should be temporarily grounded,"Senator Feinstein wrote in a letter to the FAA.

"The FAA must guarantee that all critical software updates have been delivered and pilots are well trained in their operation," Blumenthal echoed in a statement. He later told reporters on Capitol Hill that there's "no reason the FAA should be trying to save face, it's own face at the expense of air safety which is what's happening now in their refusal to ground these airplanes until they are proven safe." He later appealed that any American flier who wants to rebook a 737 Max 8 flight "should be permitted to do so without any expense."

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Romney tweeted his support of the grounding, writing "Out of an abundance of caution for the flying public, the FAA should ground the 737 MAX 8 until we investigate the causes of recent crashes and ensure the plane's airworthiness."

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. — Mitt Romney (@MittRomney) March 12, 2019

He later told reporters that it would be "common sense" to ground the aircraft. "The senate has a responsibility to help oversee the aircraft industry and this is something that I think ought to be done," Romney added. Fellow Republican Ted Cruz said it would be "prudent" for the United States likewise to temporarily ground the aircraft until the FAA confirms its safety.

He added that as chairman of the Subcommittee on Aviation and Space, he intends to hold a hearing to investigate the crash "and ensure that the United States aviation industry remains the safest in the world."

2020 contender Elizabeth Warren also joined the chorus of calls, saying in a statement that the FAA 8 should "immediately ground this plane in the United States until its safety can be assured."

American Airlines operates 24 Max 8 jets, and Southwest Airlines operates the largest U.S. fleet of these planes, with 34. Both airlines expressed confidence in the safety of the aircraft and their crews.

The FAA ordered Boeing to enhance safety-related software on all its 737 Max 8 planes by next month.

The Ethiopian flight crashed shortly after takeoff from Addis Ababa Sunday morning. More than 30 nationalities are among the dead, including at least eight Americans. The plane was new and had been delivered to the airline in November.

Other countries have already grounded the Max 8 planes, including Australia, Brazil, the Cayman Islands, China, Ethiopia, India, Indonesia, Mexico, Singapore, South Korea and the United Kingdom.

The Ethiopian Airlines Flight 302 crash was the second crash in recent months involving the new Max 8 plane. Just five months earlier, in October, a crash involving the same Boeing 737 model took place near Jakarta, Indonesia when a Lion Air flight plunged into the Java Sea minutes after taking off, killing all 189 people on board.

"These two catastrophic accidents – both claiming the lives of all on board – call into serious question the safety of these airplanes. The FAA and the airline industry must act quickly and decisively to protect American travelers, pilots, and flight attendants. These planes must be grounded immediately, and airlines should work expeditiously to minimize disruption and accommodate customers whose travel is impacted," urged Blumenthal.

Boeing said in a statement on Monday that while safety is a "core value for everyone at Boeing and the safety of our airplanes, our customers' passengers and their crews is always our top priority," and it would therefore not be mandating any further action beyond a "software enhancement" on the Max jets. Boeing went on to say that the "737 MAX is a safe airplane that was designed, built and supported by our skilled employees who approach their work with the utmost integrity."