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A video posted Monday on YouTube appears to show TSA agents testing passengers' drinks that had been purchased after passing through screening checkpoints. NBC's Tom Costello reports.

The Transportation Security Administration is under renewed criticism for its security tactics after video captured over the Labor Day weekend shows TSA agents testing passengers' drinks at an airport gate in Columbus, Ohio. But the TSA says the policy is nothing new.

The video, which a traveler at the Columbus airport captured on Sunday, shows TSA agents approaching random passengers sitting at the gate and testing their liquids.

"Now remember that this is inside the terminal, well beyond the security check and purchased inside the terminal ... just people waiting to get on the plane," wrote YouTube user "danno02." By Tuesday evening, the video had garnered more than 54,000 views and several hundred comments.

The TSA insisted Tuesday that this policy of randomly checking passengers' drinks at the gate has been going on for five years now.

As part of this process — which TSA  justifies as part of the "random, constantly changing" security profile at the nation's airports — a TSA agent uses a test strip and dropper that contains a non-toxic solution.

"(Officers) simply have the passenger remove the cap/lid and they hold the strip over the opening of the container," the TSA wrote in a blog post in July. "Procedures call for moving the test strip to the side and applying the solution from the dropper to test the strip. If the test results are positive TSA will conduct additional testing to make a final assessment."

TSA justified the random liquid testing at gates, saying they "stay away from static security tactics."

"If everything we did was always the same, it would provide a checklist for people to know exactly what to expect," TSA wrote."While this would be extremely helpful for passengers, it would also be useful to those wishing to do us harm."

After authorities thwarted a transatlantic terrorist plot involving liquid explosives in 2006, the TSA created the "3-1-1" rule. Under those measures, passengers may carry one quart-size clear plastic bag holding 3.4-ounce (or smaller) containers of liquid or gel. Since the rule took effect, purchasing beverages once through airport security has become normal for thirsty travelers.

In response to the 9/11 terror attacks, TSA implemented a number of new security measures — many of them have faced their fair share of criticism, including the use of full-body scanners that use advanced imaging technology.

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DALLAS — Conservative talk show host Glenn Beck says he was treated rudely on an American Airlines flight and will never fly on the carrier again.

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American apologized and said it's looking into the incident aboard a Labor Day weekend flight from Newark, N.J., to Dallas.

Beck said on his radio show Tuesday that a flight attendant on a New York-to-Dallas plane "treated me as a subhuman." Beck said the man "fawned over the other passengers" but "barked" at Beck and slammed a can of soda down in front of him.

Beck implied that the flight attendant singled him out because of his political views.

"My family will never choose American Airlines again ... if this is the kind of people that American Airlines likes to hire," Beck said.

American tweeted an apology, and a spokesman went a bit further.

"We are sorry for the experience Mr. Beck had on a recent flight," said spokesman Matt Miller. "The comfort and satisfaction of our customers are very important priorities to us and we take these matters seriously. We have reached out to Mr. Beck's office and are actively looking into the situation."

An aide to Beck declined to comment further or say whether the commentator had talked with American since the flight.

American, the nation's third-biggest airline, is owned by AMR Corp., which filed for bankruptcy protection in November.

Federal air safety investigators have concluded that a series of mistakes in communication led to an error that allowed commuter planes to get too close to each other in late July at Washington's Reagan National Airport.

Two commuter jets on July 31 were directed to take off the wrong way, heading toward a third commuter plane coming in for a landing on the same runway. As a result, the planes briefly lost the required minimum distance for lateral and vertical separation.

Regional air traffic controllers noticed a violent weather system south of the airport on the afternoon of July 31 and suggested a change in the normal traffic flow, which would require planes to land from the north to avoid it. That would mean changing the direction of take-offs, too, but the communication to bring that change about was fumbled, according to a report out Wednesday by the National Transportation Safety Board.

Related: 3 jets in close call never at risk of colliding, DOT and FAA say

The NTSB report says that a regional controller called the Reagan Airport control tower, talked about the planes heading in toward the storm and said, "I was wondering if we could flush them all into one-nine," using the numerical designation for landing on the main runway from the north.

But because of many conversations going on in the tower, the traffic manager who took the call said later that she thought the regional controller said runway one -- meaning operations from the south -- not one-nine. She said she assumed the regional coordinator simply wanted to speed up the pace of runway operations, not switch directions.

Because of her misunderstanding, the NTSB says, tower controllers didn't get the word. Only when they noticed the problem did they divert the incoming plane. The report also says that even though the planes got closer than federal minimums specify, "their flight paths never intersected," meaning they were never on a collision course, as some media reports at the time suggested.

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See images from the terrorist attacks of September 11, 2001.

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A U.S. judge ruled that AMR Corp's American Airlines and United Continental Holdings Inc must face trial over claims relating to the September 11 attacks that destroyed the landmark towers of the World Trade Center in New York almost 11 years ago, court documents showed.

In July 2001, two months before the attacks, World Trade Center Properties LLC (WTCP) bought 99-year leases to four World Trade Center buildings from the Port Authority of New York and New Jersey Inc for $2.805 billion.

In its lawsuit against United Airlines and American Airlines, WTCP said that had it not been for the airlines' negligence, "the terrorists could not have boarded and hijacked the aircraft and flown them into the twin towers," on September 11, 2001, according a New York court filing.

NBC News anchors and correspondents recall their personal memories of reporting live the morning of September 11, 2001 as the terrorist attacks on America unfolded and as some of the memorable stories emerged in the days and weeks that followed.

The company claimed damages of $8.4 billion from the airlines, the estimated cost of replacing the towers.

Judge Alvin Hellerstein limited the value of WTCP's destroyed property to $2.805 billion, the price WTCP paid for the leases.

The defendants denied they were negligent, and said the case should not go to trial because WTCP has recovered $4.091 billion from insurance companies.

Farooq Naeem / AFP - Getty Images

U.S. forces found and killed the al-Qaida leader in the affluent Pakistani town of Abbottabad, where he had been living in a large compound.

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Judge Hellerstein said at this stage he could not reasonably determine the defendants' claim that insurance payments received by WTCP covered the damages the company is seeking from them.

"On this record, before trial, I am not able to make such findings," Judge Hellerstein said in a court filing.

The case is in re September 11 litigation, Case No. 21-MC-101, U.S. District Court, Southern District of New York.

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