LaGuardia and Kennedy have the most arrival delays among the nation's biggest airports, with more than 40% of the lags due to crowded skies and weather -- according to an analysis of federal data released by an air travel advocacy group.

Millions of passengers traveling through New York City airports face airspace-related snags, which range from heavy air traffic and congestion to non-extreme weather like fog.

Newark fliers have felt the pain as well, with crowded airspace and weather causing 35% of its delays, the airport advocacy group Global Gateway Alliance said.

In an analysis of the 29 biggest airports in the U.S. covering January to April of this year, LaGuardia ranked last in on-time performance; Kennedy ranked 28th and Newark registered 24th, the report said. Only 65% of flights arrived on time at LaGuardia, the worst in the country.

The New York airspace is the most crowded in the country, the report says.

The heavy volume of air traffic is responsible for about one-third of airspace delays -- and affected more than 3,500 flights at JFK, LaGuardia, and Newark, U.S. DOT Bureau of Transportation Statistics data shows.

The department only breaks down the causes of delays for arrivals.

More than 315,000 flights arrive at New York airports every year.

Setbacks from non-extreme weather, such as rain and fog, are categorized as an "airspace delay" because they impact operations and can be remedied by airspace improvements, according to the U.S. DOT.

"Common weather conditions, such as rain and fog, are the cause of too many delays at New York area airports, highlighting the congestion in our airspace and the need for the FAA to finally bring air traffic technology into the 21st century," said Joe Sitt, chairman of the Alliance, in a statement.

The Port Authority said that Kennedy, LaGuardia and Newark are in one of the busiest and most complex airspaces in the world -- and that an issue like poor weather can cause delays to compound quickly.

"The Port Authority has made significant efforts to improve movement of planes on the ground, such as installing high-speed taxiways to help move planes faster on and off runways and a timed metering system at JFK that keeps planes at gates longer to reduce waits on the airfield," the Port Authority said in a statement.

Another major source of woe for passengers flying into the New York area is a late flight snarling the arrival or takeoff of another flight -- often because of congestion.

This has caused almost 2,700 flights to be held up at Kennedy through the end of April -- or 34% of delays, the analysis shows.

At LaGuardia, it affected 2,663 trips and represented 28% of delays.

Airline delays, which range from crew to baggage problems, also snagged flights.

They delayed more than 1,800 flights at JFK through the end of April, and represented 21% of all flight delays.

At LaGuardia, they affected more than 2,300 flights and were responsible for 24% of flight delays.Security issues snagged 11 flights at LaGuardia and six at Newark.

The Global Gateway Alliance is calling for satellite technology, called NextGen, to fully replace radar at New York City airports, as well as for longer runways and more gates. Some NextGen technology, such as curved approaches to airports, has been introduced in New York but is not being widely used yet, according to the U.S. Department of Transportation inspector general

"When passengers have better navigational technology on their phones than most pilots do on their planes, the result is chronic delays from weather and congestion in the skies," added Sitt.

The Alliance also wants to see the creation of a NY Airport Delay Council of outside and industry experts that would monitor and report on the region's airspace -- and an air traffic control office that is independent of the FAA.

The Port Authority added that it has spent almost $200 million to add capacity at its airports and reduce delays, and has advocated for more federal spending for NextGen satellite technology.