The 10 biggest US airlines have warned that the impending switch-on of 5G mobile phone services will cause "major disruption" to flights.

They said the start of Verizon and AT&T 5G mobile phone services, planned for Wednesday, would cause a "completely avoidable economic calamity".

Airlines fear C-band 5G signals will disrupt planes' navigation systems, particularly those used in bad weather.

The warning was issued in a letter sent to US aviation authorities.

The chief executives of American Airlines, Delta Air Lines and United Airlines were joined by others in saying: "Immediate intervention is needed to avoid significant operational disruption to air passengers, shippers, supply chain and delivery of needed medical supplies", including vaccine distribution.

The BBC has seen the letter outlining their urgent concerns. It was sent to Transportation Secretary Pete Buttigieg, as well as the head of the Federal Aviation Administration (FAA), the chair of the Federal Communications Commission and the director of the National Economic Council.

The BBC understands that negotiations are continuing at the highest levels of the US government about what has been described as a "very fluid situation".

The airlines want 5G signals to be excluded from "the approximate two miles of airport runways at affected airports as defined by the FAA on 19 January 2022".

"This will allow 5G to be deployed while avoiding harmful impacts on the aviation industry, travelling public, supply chain, vaccine distribution, our workforce and broader economy.

"We further ask that the FAA immediately identify those base stations closest to key airport runways that need to be addressed to ensure safety and avoid disruption," they added.

These concerns were recently highlighted by the two big planemakers, Airbus and Boeing, in a rare joint warning.

The group of airlines said: "Airplane manufacturers have informed us that there are huge swathes of the operating fleet that may need to be indefinitely grounded.

"In addition to the chaos caused domestically, this lack of usable wide-body aircraft could potentially strand tens of thousands of Americans overseas."

In an update on Sunday, the FAA, which oversees aviation safety across the US, said it had cleared "an estimated 45% of the US commercial fleet to perform low-visibility landings at many of the airports where 5G C-band will be deployed".

The FAA added that it had approved "two radio altimeter models that are installed in a wide variety of Boeing and Airbus planes".

"Even with these new approvals, flights at some airports may still be affected," the regulator said.

"The FAA also continues to work with manufacturers to understand how radar altimeter data is used in other flight control systems. Passengers should check with their airlines if weather is forecast at a destination where 5G interference is possible."

Phone companies have spent tens of billions of dollars on upgrading their networks to deploy the 5G technology, which brings much faster internet services and greater connectivity.

There have been several delays already because of the aviation concerns, with launch dates in December and earlier this month both being pushed back.

US wireless industry group CTIA has previously said 5G is safe and accused the aviation industry of fearmongering and distorting facts.

"A delay will cause real harm. Pushing back deployment one year would subtract $50bn in economic growth, just as our nation recovers and rebuilds from the pandemic," said CTIA chief executive Meredith Attwell Baker in a blog post in November.