United Airlines CEO Scott Kirby on Monday sought to reassure customers about the carrier’s safety after a series of flight problems in recent weeks.

In one incident this month, a tire fell from one of the carrier’s Japan-bound Boeing 777s shortly after takeoff, damaging cars in a San Francisco airport parking lot. In another, a missing panel from the plane was discovered after the older Boeing 737 landed in Oregon on Friday.

“Safety is our highest priority and is at the center of everything we do,” Kirby said in an email to customers. “Unfortunately, in the past few weeks, our airline has experienced a number of incidents that are reminders of the importance of safety.”

Kirby said the incidents, which the Federal Aviation Administration is investigating, were “all unrelated” but that the team is reviewing the details “and using those insights to inform our safety training and procedures across all employee groups.”

The string of recent mishaps occurred during heightened scrutiny of the aviation industry after a door plug panel blew off an Alaska Airlines‘ nearly new Boeing 737 Max 9 on Jan. 5.

On March 8, a United 737 Max plane rolled off a Houston runway. On March 4, a United Boeing 737 that was heading to Florida from Houston returned to the airport after the engine ingested plastic bubble wrap, with video on social media showing flames coming out of the engine.

United’s CEO said the airline had already planned to implement changes such as “an extra day of in-person training for all pilots starting in May and a centralized training curriculum for our new-hire maintenance technicians.”

“You can be confident that every time a United plane pulls away from the gate, everyone on our team is working together to keep you safe on your trip,” Kirby wrote.