In just the last few weeks, Delta and Southwest each experienced massive system-wide outages that grounded thousands of flights and ruined travel plans for countless passengers — and there are reasons to believe it could happen to other carriers. Now some lawmakers want the airlines to answer for these failures and to explain what’s being done to prevent future shutdowns.

Following the most recent outages, airline security experts explained that a number of carriers are using decades-old systems to track reservations. When one of these antiquated platforms go down, it can cause a huge number of delays and cancellations as the airline tries to sync the old system up with the rest of the airline’s network.

In letters sent to Delta, Southwest, and eleven other U.S. carriers, Senators Ed Markey (MA) and Richard Blumenthal (CT) raise concerns about the vulnerability of these ancient systems — not just to power outages or hardware glitches, but to attacks from hackers and cybercriminals.

The issue is all the more pressing, note the senators, because so much of the U.S. airline industry has been consolidated in the hands of so few national operators.

“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,” explains the letter. “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.”

During the Delta outage, it was revealed that consolidation and policy changes have made it more difficult for airlines to get their stranded passengers onto planes operated by competing carriers.

“As a result, airlines may not be providing passengers with the full range of options available during travel disruptions,” explains the letter. “We believe that, in the event of flight delays and cancellations caused by airlines, air carriers should rebook interested passengers on another airline or on a different mode of transportation without charging consumers additional costs or fees.”

The senators have given the airlines until Sept. 16 to respond to a number of requests for information, including:

• A list of IT outages and disruptions that resulted in flight cancelations or delays in the last five years, along with notes on what caused the problem, why existing safeguards failed, and what changes have been implemented as a result.

• Data on how many passengers were affected by these delayed or canceled flights. How many were eligible for rebooking on other carriers, and how many of those were actually rebooked?

• Additionally, does the airline let travelers know they are eligible to rebook elsewhere in these cases? And does the airline refund any difference between the cost of the two tickets?

• Details on existing safeguards against outages and backups in the case of power outages, glitches, and online attacks.

• Descriptions of current IT systems and the age of the software used. Explanations on how mergers with other carriers have affected IT systems and updates.

• What compensation — refunds, food, lodging — does the airline make available to travelers stranded by IT outages?

In addition to Delta and Southwest, Markey and Blumenthal sent letters to American Airlines, United Airlines, JetBlue, Alaska Airlines, Spirit Airlines, Frontier Airlines, Hawaiian Airlines, Allegiant Air, Virgin America, Sun Country Airlines, and Island Air Hawaii.

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