On Monday, the first business day after budget cuts forced the furlough of air traffic controllers, the on-time performance of the nation's airlines dropped nearly 10%.
That was a finding based on statistics compiled by Flightstats.com, a website that monitors airline performance rates.
To cut more than $600 million called for under federal sequestration, the Federal Aviation Administration ordered air traffic controllers and others to take one day off work in every two-week period. The job furloughs began Sunday.
The move cut the staff of nearly 15,000 controllers by about 10% on any given day.
The FAA has warned that during heavy air traffic it will order planes to remain grounded until air traffic controllers can bring order to the congestion.
On Sunday, the FAA said it delayed 400 flights because of staff shortages in air traffic control towers.
At the nation's largest airports, 80.81% of all flights arrived on time, almost the same rate as the previous Sunday, according to Flightstats.com.