Travelers aren't the only ones frustrated over a wave of flight cancellations that have snarled travel plans across the Northeast. One airline executive is also grumbling about the disruptions.

United Airlines CEO Scott Kirby blasted the Federal Aviation Agency's decision to cancel thousands of flights last weekend due to a severe bout of weather. The cancellations and delays have affected more than 150,000 United customers, according to the company — and that number is only growing as the delays continue into Wednesday.

In an email to employees that was sent on Monday, Kirby says the FAA "failed" United Airlines by ordering flight cancellations and delays at Newark Liberty International Airport amid difficult weather conditions that it "has historically been able to manage." 

"I'm … frustrated that the FAA frankly failed us this weekend," Kirby said in the email. "As you know, the weather we saw in EWR is something that the FAA has historically been able to manage without a severe impact on our operation and customers."

The FAA oversees air traffic in the U.S., giving it influence over flight schedules. In response to Kirby's criticisms, the FAA said in an email to CBS MoneyWatch, "We will always collaborate with anyone seriously willing to join us to solve a problem."

Nearly 700 flights into and out of the U.S. were cancelled as of Wednesday morning, data from flight tracker FlightAware shows. Of those flights, 68, or roughly 10%, were flying to or from Newark Liberty International Airport, which is United Airlines' New York-area hub.

However, some travelers at Newark Airport took to social media to vent about delays — and many placed the blame on United Airlines, not the FAA, saying that the airline didn't have enough staff on hand to help stranded customers. United didn't immediately return a request for comment.

One person at Newark reported on Wednesday that Terminal C was "absolutely insane" with a nine-hour line at the help desk.

"Come on @UnitedAirlines, 9 hours and counting in a queue for Customer Service at Newark Airport following cancellation of my flight just before 10pm yesterday. I think you need more staff to help sort this backlog ..." one traveler wrote on Twitter on Tuesday morning.

Another traveler tweeted, "No hotel, no compensation, no apologies; only told to join a +/-1000 people line to get a voucher or another fake booking for the next flight and wait for that to also be canceled!?"

Air traffic controller shortage

In recent months, the FAA has struggled to carry out its duties due to staff shortages. In March, the FAA issued a notice warning that an air traffic controller shortage at its New York facility could disrupt summer travel. According to that notice, the agency had reached just 54% of its staffing goal for certified professional controllers at that location — far below the national average. Workers at the facility provide air traffic services for John F. Kennedy International Airport, LaGuardia Airport and Newark Liberty International Airport, according to the FAA. 

Kirby told his employees he will work in tandem with the FAA and the Department of Transportation to prevent a similar situation from disrupting travel this summer, according to the email. However, he stressed that the responsibility to remedy the FAA's issues lies with the agency itself.  

"It's not the fault of the current FAA leadership that they are in this seriously understaffed position — it's been building up for a long time before they were in charge," Kirby wrote. "But, it is incumbent on them now to lead and take action to minimize the impact."

In:
• Federal Aviation Administration
• United Airlines
• Newark Liberty International Airport