NEW YORK (AP) — An Osprey being used to ferry White House staff and government officials from an event in New York on Monday was grounded due to a safety concern, with one witness reporting flames under the right engine.

The staff and officials were removed from the aircraft, part of the Marine Corps HMX-1 presidential helicopter fleet, and transferred to a second Osprey to continue their trip accompanying President Joe Biden at a “Friendsgiving” event with members of the U.S. Coast Guard in Staten Island.

The issue caused only a minor delay for Biden’s return to Washington on Monday evening.

The incident occurred the same day lawmakers sent a letter to Defense Secretary Lloyd Austin asking him to re-ground the military’s entire fleet of V-22 Ospreys until solutions can be put in place to address safety and design issues identified by The Associated Press in its recent in-depth investigation of the aircraft’s accident record.

The Marine Corps did not immediately respond to a request for comment on the New York incident. A journalist traveling with the president reported seeing a fire under the right engine shortly before staff were notified the Osprey would be grounded.

It's not the first time White House staff or reporters have had to be removed from an Osprey during a trip due to safety concerns. In November 2023 an Osprey ferrying White House reporters and staff returned to the ground shortly after takeoff after four loud “pops” were heard and smoke was seen.

In the letter sent Monday to Austin, Sens. Elizabeth Warren and Ed Markey, and Rep. Richard Neal, all Democrats from Massachusetts, said that “given the current concerns about the safety of the V-22, the aircraft should be grounded, and should not be deployed again until the platform’s significant deficiencies are fully addressed."

The Osprey, which flies like both a helicopter and an airplane, has been in more than 21 major accidents, many of which can be tied back to choices made in its design, the AP found.

The whole fleet was grounded for three months this year following a deadly crash in Japan in November 2023 that killed eight service members, including one from Massachusetts.

Ospreys, which are operated by the Navy, Air Force and Marine Corps and used in the presidential fleet, have now returned to flight operations, with some restrictions.

Osprey pilots have told the AP they do not want to see the aircraft grounded, despite safety concerns, because of its unique capabilities. Program officials have said they are working on fixes to improve the V-22's safety and reliability.

The Pentagon did not immediately respond to a request for comment on the letter.

The lawmakers also cited the AP's reporting that pilots are having to push the V-22's “interim power” feature to be able to land safely — but are advised against it because it can wear down parts. Interim power was a factor in the most recent accident in October when a Japanese self-defense forces Osprey violently tilted and struck the ground on takeoff. An investigation determined the pilots were to blame for not turning on the interim power during takeoff.

“The reality for pilots is that they have to push the aircraft to its limits to stay safe,” the lawmakers wrote.

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Copp reported from Washington. Associated Press writer Zeke Miller contributed to this report.