Atlanta (CNN) — Get ready, America, for a summer full of long security lines at major airports, missed flight connections and millions of grumpy passengers.

That's the warning from authorities at the nation's most congested and busiest airports and the Transportation Security Administration.

Airports are starting to take matters into their own hands.

In an unusual, strongly worded letter to the TSA, the Port Authority of New York and New Jersey -- which oversees the New York City area's three major airports -- has essentially threatened to fire the TSA by privatizing their passenger screening process.

Atlanta's Hartsfield-Jackson airport -- which handled more than 100 million travelers last year -- sent a similar letter to the TSA threatening to privatize passenger security lines

That airport is partnering with Delta Air Lines and the TSA to figure out a better passenger screening procedure.

They're calling these experimental lines Innovation Lines -- or I-Lines.

Two I-Lines are expected to debut at Atlanta's south domestic terminal checkpoint on May 24, the TSA said. Here's how they'll be different:

Baggage bins automatically move to a separate conveyor belt if a TSA agent IDs them as suspicious.

Baggage bins automatically recirculate after they move through the security machine.

The I-Line includes special "divestiture" areas where passengers can take off shoes, belts, etc. at their own pace.

"All of these things will save time," he said. "We just don't know how much time."

The biggest time saver, Wolf said, likely will be re-routing suspicious bags.

"Re-routing bags to a different conveyor is a big deal," he said. "Once that belt stops, the whole line stops."

The X-ray machine that screens passenger bags is a "big time suck," Wolf said.

The decision that goes into stopping the belt and flagging a bag for extra scrutiny takes time and holds up the line.

The new equipment is similar to systems employed at London's Heathrow and Amsterdam's Schiphol, the TSA said.

The I-Lines will operate side-by-side with two regular lanes. Officials will gather data to compare and analyze the two systems.

The results will help the TSA create a pilot program that could be replicated at other airports.

The New York/New Jersey Port Authority letter to the TSA mentioned the "inadequacy of TSA passenger screening," fears of widespread "customer dissatisfaction" and described wait times as "abysmal."

From mid-March to mid-April, there were hundreds of times that passenger waits lasted more than 20 minutes -- and sometimes more than 55 minutes, the letter said.

"The patience of the flying public has reached a breaking point," said the letter from Port Authority Aviation Department Director Thomas Bosco and Chief Security Officer Thomas Belfiore.

The airspace surrounding New York's John F. Kennedy International Airport, LaGuardia Airport and New Jersey's Newark Liberty International Airport ranks among the most congested in the nation. About 126 million passengers passed through those airports last year.

The TSA has already warned that staffing issues might create long waits at the nation's big airports during the upcoming summer travel season.

Homeland Security Secretary Jeh C. Johnson said he has called on Congress to approve more money to pay overtime for TSA officers working at airports across the nation this summer.

So far, that hasn't happened.

Factors like relatively lower fuel prices and fares are likely to drive passenger traffic higher this summer.

As for the carriers, American Airlines has blamed missed flights by thousands of its passengers on the TSA checkpoints.

The airline lobbying group Airlines for America has kicked off an aggressive social media campaign asking people to share photos of long security lines and post them with the hashtag: #iHatetheWait.

But what happens after passengers pass through the metal detectors and put their shoes back on and get on the planes and settle into their seats?

Apparently, a lot of us are able to put that unpleasantness behind us, according to a recent survey.

Satisfaction with North American airlines rose for a fourth straight year, measuring at a record high 726 points on a scale of 1,000.