United Airlines transatlantic flight cancelled three days in a row

Something unusual is happening with United Airlines. Just days after flight UA507 from San Francisco to Rome was either cancelled or diverted three times in a row, a similar situation occurred with flight UA942 from Washington Dulles to Lisbon, which was cancelled on three consecutive days between August 16 and 18.

One of the cancellations even involved a midair diversion, with the plane turning back to the departure airport 2.5 hours into the flight while over the Atlantic Ocean.

In the earlier incidents, the aircraft involved was a Boeing 777-200ER. However, in the most recent cases, the cancellations affected two Boeing 767-400s and a Boeing 757-200.

It raises the question: what exactly is going on with the airline?