Of all the competing regulation issues for car service app Uber, airport-related rules may be some of the most complex and inconsistent.

Airport pickup policy varies widely by city. As of November, only 58 of the 224 cities where Uber operates allowed airport pickups. Other airports only allow Uber pickups in certain terminals, or don't allow curbside pickups.

Many Uber drivers go to airports for rides anyway, but regulators don't take the actions lightly. In January, LA Weekly reported Los Angeles police had issued around 500 tickets to Uber and Lyft drivers for illegal pickups since 2013.

Perhaps with this in mind, in recent months Uber has implemented a virtual geofence at some airports. It requires drivers to wait in a specified area outside airport property in order to receive ride requests from passengers. The policy helps prevent traffic congestion near airports caused by Uber cars swarming around waiting for customers.

Initially, the queue system went by proximity, matching the customer to the nearest driver when they request a ride. But Uber has been slowly updating the system to a first in first out policy, so as soon as a driver enters a specified area near the airport they are placed in a virtual queue.

One Charlotte driver posted a? message he received from Uber to a forum for Uber drivers on Reddit about six months ago.

"Effective immediately, airport requests will be issued to you, our partners, on a first-come, first-serve basis. When you enter designated areas (see below) you will be placed into the queue to accept requests for trips from the airport."

At the time, some drivers on the ?forum welcomed it.

"I hope this is implemented everywhere. At least it'll make it worthwhile to sit around at an airport knowing that you'll get a call eventually as you move up the line," one person wrote.

But six days ago, another Reddit user posted to an Uber forum on the site saying "DC Drivers- New airport "virtual queue" makes it nearly impossible to get an airport pickup."

"This is bullshit policy," another user wrote. "The area is so big for an airport pickup that a friend of mine waited two hours for a Dulles call before he gave up. For a lot of us, it's a great way to get paid to drive into the city and then stay there for the surge. I'm completely frustrated by this."