Canceled flights and widespread unease about outdated tech and air traffic controller staffing shortages had a pretty substantial impact on Newark Liberty International Airport’s traffic numbers last month. Passenger volume plunged 20% year over year at the airport in May, according to Port Authority officials at a Thursday meeting.

Back-of-the-napkin math puts that reduction at about 880,000 passengers whose flights were either canceled or who decided against flying out of Newark during the stretch.

The airport’s struggles are expected to weigh heaviest on United Airlines, which controls more than 70% of Newark’s passenger traffic. The airport represents about 20% of United’s revenue, and analysts expect its spring woes to ding United’s bottom line in the second quarter. United cut about 35 flights from its daily schedule at Newark last month.