Airports across the East Coast, including those around New York City, are under an advisory warning that poor weather combined with new 5G airwaves could lead to flight diversions.

The U.S. Federal Aviation Administration Thursday morning posted the list of airports—which also include several in the West—on its air-traffic advisories website. A storm bringing rain and snow extends across much of the East Coast.

The weather systems are the first major test of how the air-traffic system will perform after 5G went live Wednesday. A last-minute accord between wireless telephone companies and the FAA on 5G averted major disruptions but didn’t eliminate them, and the focus is now on a long-term solution for a nationwide rollout of the technology.

The FAA warning Thursday was attributed to the 5G expansion and potential for radio altimeter interference, according to the website. Certain low-visibility landings can’t be performed in the presence of 5G signals on aircraft at risk of interference.

The airports listed included New York’s LaGuardia and John F. Kennedy; Newark Liberty and Teterboro in New Jersey; Boston; Hartford, Connecticut; Providence, Rhode Island; Philadelphia; Baltimore/Washington; San Francisco and Oakland, California; and Salt Lake City.

The FAA on Wednesday said as many as 62% of aircraft were equipped with altimeters that were shielded from 5G and weren’t subject to flight restrictions. An agreement by AT&T Inc. and Verizon Communications Inc. earlier this week to create wider 5G buffer zones around U.S. airports has also lessened flight restrictions, the FAA said.

The FAA aircraft exemptions include the vast majority of large jets, but none of the U.S. regional jet fleet—aircraft carrying roughly 50 to 90 passengers—have yet to receive such FAA clearance.

The faster wireless service began in dozens of communities across the country on Wednesday. So far, disruptions to the aviation system have been minimal.