When low-cost carrier Avelo Airlines launched the first of 11 new routes to small cities and secondary airports from 14-gate Hollywood Burbank Airport in April, it raised the airport’s profile as an alternative to Los Angeles International — and put a spotlight on the its outdated facilities.

“The existing terminal is too close to the runways and taxiways — and the building is now 91 years old,” Frank Miller, the airport’s executive director, told NBC News. A terminal replacement plan put on hold due to Covid-19 is back on track, but funding sources for this — and for other airport infrastructure projects around the country — are “simply inadequate,” Miller said.

Even before the pandemic and the sharp decline in air travel, “chronic underfunding” created a backlog of more than $115 billion in necessary infrastructure needs for just the next five years, according to a recent study from Airports Council International – North America (ACI-NA).

“We’re trying to build 21st-century airports,” said Kevin Burke, ACI-NA’s president and chief executive officer. “But we have 20th-century airports that are, on average, more than 40 years old.”