LINTHICUM, Md. (WJZ) — There are growing calls for the Federal Aviation Administration to ground Boeing 737 Max-series aircraft amid safety concerns following two deadly crashes in five months.

As of Tuesday, only carriers in the United States and Canada continued to fly the planes.

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At BWI-Thurgood Marshall Airport, WJZ Investigator Mike Hellgren watched several 737 Max planes land Tuesday afternoon.

Keith Franz, an aviation attorney based in the Baltimore area, says the planes should be grounded immediately.

“The safety of an unsuspecting public requires that they get a clear handle on why this is happening before they just give carte blanche to the airlines to continue to fly these planes,” Franz said. “Enough has happened that is similar between these two crashes to warrant a more in-depth investigation as to why.“

The European Union grounded the plane, the latest entity to do so after the Ethiopian Airlines crash that killed 157 people on Sunday.

That disaster came just five months after a similar Indonesian Lion Air jet plunged into the ocean, killing 189.

The FAA, however, said late Tuesday afternoon it has found “no systemic performance issues and … no basis to order grounding the aircraft.”

The FAA said it expects Boeing will soon complete improvements to an automated anti-stall system suspected of contributing to the Lion Air crash in October and update training requirements and related flight crew manuals.

Although experts warn that it’s too early to know what caused the Ethiopian Airlines crash, both crashes occurred shortly after takeoff, suggesting a possible connection CBS News reports.

Other concerns are focusing on the Max aircraft’s software that’s designed to automatically adjust a plane’s flight angles when they’re too steep.

Boeing issued this statement.

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Lawmakers on both sides of the aisle support ground the planes for now.

“The FAA must guarantee that all critical software updates have been delivered and pilots are well trained in their operation,” Sen. Richard Blumenthal (D-Connecticut) said. “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.”

Republican Senator Mitt Romney of Utah 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.”

The 8 denotes the size of the plane. There are also Max 9 and Max 10 aircraft.

Southwest has 34 of the planes in its fleet and has maintained they are safe.

“I would suggest anyone check before they go to the airport and see if their plane is a 737 Max and if they’re uncomfortable they should switch planes,“ attorney Franz said. “Certainly, it’s understandable people would have great concern if they are scheduled to fly in this aircraft.“

Southwest responded to one concerned customer on Twitter with this: “The Safety of our Customers always comes first, and we understand your concern. You can check which aircraft will be operated for a given flight by clicking on the flight number during the booking process, so that you can choose the type of aircraft you wish to fly on.”

Unions representing flight attendants have called for the planes to be grounded temporarily.

“I believe Boeing is putting significant pressure on the FAA and the airlines to keep those planes aloft,“ Franz said.

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