A pair of U.S. senators from New England are seeking answers from more than a dozen U.S. airlines in wake of a series of widespread flight cancellations and delays brought on by information technology systems issues.

Senators Edward J. Markey (D-Mass.) and Richard Blumenthal (D-Conn.) sent letters to 13 major airlines Tuesday, including American Airlines, Delta Air Lines, Southwest Airlines, United Airlines, JetBlue and Alaska Airlines, among others.

“We are concerned with recent reports indicating that airlines’ IT systems may be susceptible to faltering because of the way they are designed and have been maintained,” the senators wrote in the letter sent to the airline CEOs. 

The letters come on the heels of a crippling computer outage that forced Delta to cancel thousands of flights last week. Last month, a router failure was blamed for hundreds of canceled Southwest flights.

“Some airlines use older technology, including software from the 1960s, as the backbone of their operations in 2016,” added Markey and Blumenthal. “Not only may these IT systems be more prone to failure, but they may also be vulnerable to cyberattacks.”

In the letter, Markey and Blumenthal, who are both members of the Senate Commerce, Science and Transportation Committee, present 10 questions to the airline CEOs.

“What specific safeguards and backups does your company have in place to prevent your airline’s IT systems from failing?” the senators ask.

In addition to the current state of airlines’ IT systems, Markey and Blumenthal express concern over carriers’ policies for assisting customers in the event of cancellations and delays resulting from system errors. “What other compensation and recourse…does your airline provide consumers in the event of delays and cancellations caused by the air carrier?”

Markey and Blumenthal requested responses to the inquiries no later than Sept. 16.

“Now that four air carriers control approximately 85 percent of domestic capacity, all it takes is one airline to experience an outage and thousands of passengers could be stranded, resulting in missed business meetings, graduations, weddings, funerals, and other prepaid events,” the letters state.

“In light of these recent technology issues, we encourage you to ensure that your IT systems have the appropriate safeguards and backups in place to withstand power outages, technological glitches, cyberattacks and other hazards.”

This isn’t the first time Markey and Blumenthal have challenged airlines.

In March, the duo introduced the Forbidding Airlines from Imposing Ridiculous (FAIR) Fees Act designed to limit various airline fees and as recently as May they urged airlines to waive baggage fees to reduce congestion at airport security checkpoints.