DALLAS — Federal officials cited the surge of incidents involving disruptive and sometimes violent passengers in resuming self-defense training for airline flight attendants and pilots.

The classes, which are voluntary for airline flight crews, were halted last year because of COVID-19. The Transportation Security Administration said they will resume in early July.

The move was praised by leaders of major flight attendant unions, who lobbied to create the training programs after the terror attacks of Sept. 11, 2001. The terrorists who hijacked and crashed four planes attacked several flight attendants and passengers before storming the cockpits.

“Since a flight attendant was the first to perish, we wanted to make sure that we could protect ourselves from physical altercations, on and off the aircraft,” said Lyn Montgomery, president of the union local that represents Southwest Airlines flight attendants. “Right now it’s really needed, it’s incredibly valuable.”

The Federal Aviation Administration said this week that airlines have reported more than 3,000 incidents involving unruly passengers since Jan. 1, with many involving passengers who refuse to comply with a federal requirement to wear face masks. The agency did not track such reports in prior years, but a spokesman said it was safe to assume this year’s numbers are the highest ever.