WASHINGTON, Feb 23 (Reuters) - Corey Lewandowski, a top aide to the U.S. Homeland Security Secretary, entered the cockpit of a government plane uninvited during a flight last year, then fired a pilot for not having a blanket in place, two people familiar with the matter said.

The two individuals, who requested anonymity to discuss internal government operations, added that Lewandowski, a longtime ally of President Donald Trump, was traveling with Homeland Security Secretary Kristi Noem when they discovered her blanket was missing.

New details about the pilot incident suggest that Lewandowski may have violated safety guidelines set by the U.S. Coast Guard, which operated the aircraft.

One of them said that Lewandowski entered the cockpit before the plane reached an altitude of 3,048 meters (10,000 feet) and at a time when the seatbelt sign was still illuminated.

Federal Aviation Administration (FAA) regulations, several of which were tightened after the September 11 attacks, impose strict restrictions on cockpit access and prohibit interference with flight crew duties. FAA regulations also prohibit airline pilots and personnel from engaging in unnecessary activities or conversations in the cockpit while flying below 10,000 feet. Civil aircraft operators who violate this rule may face fines of thousands of dollars, while pilots may face fines or termination of employment.

The U.S. Coast Guard is not legally subject to the Federal Aviation Administration's regulations, known as the "Sterile Cockpit Rule," but it applies a similar policy, explaining in its 2021 Operations Manual, "No person may engage in any conversation or activity that could distract or interfere with the proper performance of assigned duties by flight crew members during critical phases of flight."

The manual does not specify a particular penalty for violating the rule, but it does state that rule violations will generally be dealt with through internal disciplinary procedures.

In response to a Reuters request for comment, Lewandowski said in a text message, "There was no conversation in the cockpit during takeoff."

Lewandowski added that the facts cited by the two sources were incorrect, but he did not answer a question about whether he entered the cockpit during the plane's ascent while it was still below 3,048 meters.

Aviation safety experts consider the initial takeoff to be one of the most dangerous parts of the flight.

Randy Klatt, an aviation safety officer at the Aviation Safety Foundation, said that aircraft are "low and slow" during the initial climb to 3,048 meters, making it important for pilots to focus on flight operations.

The U.S. Department of Homeland Security and its Coast Guard declined to comment on the flight in question. They did not respond to a Reuters request for interviews with the pilots. The Federal Aviation Administration did not respond to a request for comment.

The sources said that Lewandowski asked, when the pilot returned to the cockpit later in the flight, who should be separated because Noim's blanket had been left behind when the plane was changed for technical reasons before takeoff.

The two sources said the pilot, a seasoned veteran with a long service record, took responsibility for any possible error and immediately fired Lewandowski, confirming a report by the Wall Street Journal.

However, the sources said that once Noem and Lewandowski reached their destination, Coast Guard leadership realized the pilot would need to return them to the Washington area and reassigned him. The Department of Homeland Security and the Coast Guard declined to comment on the pilot's termination and reassignment. Reuters was unable to independently verify the reason for his reassignment.