United Airlines suggested Wednesday that an air traffic controller shortage is to blame for “significant delays” at its Newark Liberty International Airport (EWR) hub, as people in the U.S. began their holiday travel.

The lawmakers stressed that while progress has been made in addressing aging ATC systems, gaps in oversight remain. They criticized the FAA’s acquisition oversight council for inconsistencies in assessing high-risk factors, which they argue hinder the timely and cost-effective delivery of modernization projects.

The airline said the Federal Aviation Administration has been forced to reduce traffic flows to Newark hub because of low staffing on 12 of the first 25 days of November, disrupting more than 343,000 United travelers by delays,

The airline is citing delays at its Newark hub saying more than 348,000 passengers have been disrupted by delays since the start of November due to the air traffic controller shortage.

United Airlines said Tuesday that an acute shortage of air traffic controllers was causing “significant disruption” for travelers at its busy Newark, NJ, hub outside of New York City. The airline said the Federal Aviation Administration has been forced to reduce traffic flows to Newark hub because of low staffing on 12 of the first 25 days of November,