WASHINGTON (Reuters) -United Airlines said on Monday it has delayed the start of two new international routes, citing a pause on some certifications by the U.S. Federal Aviation Administration (FAA)for the carrier following a series of safety incidents.

The impacted routes are between Tokyo and Cebu, the Philippines, and Newark, New Jersey and Faro, Portugal, the carrier said.

The FAA said last month it was increasing its oversight of United following a series of recent safety incidents.

On March 23, the FAA said it would initiate a formal evaluation to ensure the Chicago-based airline was complying with safety regulations and said the FAA may delay future United certification projects "based on findings from oversight."

Reuters reported last month the FAA could potentially not approve allowing customers on United's new planes or new routes. The FAA did not immediately comment on United's announcement on Monday.

The Air Line Pilots Association (ALPA), the union representing United pilots, said earlier that the formal FAA evaluation is a type of audit that U.S. carriers undergo every few years and United most recently had one in 2018.

United has experienced several safety incidents in the past few months. On March 15, an external panel was found missing from a United aircraft when it landed in Oregon, prompting an FAA investigation.

United said last month that over the next several weeks employees will see more of a presence by the FAA "in our operation as they begin to review some of our work processes, manuals and facilities."