By Investigator Lisa Fletcher ABC15.com It's what you have to do when you fly - use X-ray machines, metal detectors, and deal with liquid restrictions in your carry-on luggage. You know the drill. Security checkpoints are just part of travel these days. They're supposed to keep us safe, so we use them - but not all of us and not all the time. We've discovered a 4.5 hour time frame each night when virtually anything can be brought into the secure side of Phoenix Sky Harbor Airport. There's no metal detector, no X-ray machine, and it's apparently not a problem. Afraid to show her face, one long time Sky Harbor employee talks about the security most people don't see. Lisa Fletcher: "You're telling me Sky Harbor's not safe?" Employee: "I'm telling you Sky Harbor's not safe and hasn't been for a long time." It's what we discovered in the middle of the night - TSA agents going away, and security guards taking over. It's 4.5 hours - every night - when an employee badge becomes an all-access pass. Night after night, our hidden cameras captured what security experts tell us is a disaster waiting to happen. The X-ray machines were off, the metal detectors were closed, and bags with unknown contents were carried to the secure side of the airport where the planes are. We watched as a security guard let people with purses, coolers and suitcases walk right through - bags unchecked. Even more surprising, some of the people you trust to keep you safe planned it this way. Larry Wansley is widely regarded as one of the nation's top airline security experts. "It's a frightening situation, I've just simply never seen anything like it," he said. "I really honestly have not." He's the former head of security for American Airlines, and currently consults the U.S. Government and airports around the world. We brought him in to take a look at what we found. "It is not security," he said. "It truly is not security. Anything can be going through there. I don't get it." Larry watched for hours and saw the same thing we did - guys with huge backpacks showing their ID and walking through without ever opening their bags. A flight attendant, with three suitcases in tow, flashed her badge and breezed by. A huge load of newspapers on a cart was also pulled right passed the guard and a floor cleaner was pushed by without any inspection. Even a guy with his bike just showed his ID and was able to ride through with his crate on the back, never checked. In the time we watched, dozens made it past this checkpoint, bags unchecked. Larry Wansley couldn't believe it. Clearly this is a very, very imminently dangerous situation," he said. "You've got the front door, TSA that has locked it up for the better part of the day, the majority of the day. And then you throw open the back door to be exploited by those that would simply destroy us. And I simply do not understand it and I'm appalled. I'm shocked and I'm amazed." The airport employee we talked with said she is afraid. "No one's doing anything about it," she said. "Management knows. I know management knows. I know my superiors know. I know the security guards know. Everybody knows what's going on, but nobody's doing anything about it." You would think the director of Sky Harbor, or even a spokesperson from the TSA, would trip over themselves to talk about this issue, but you would be wrong. All of them have refused on camera interviews to talk about the kind of security they've employed to keep us safe. Updated Video: Watch Phoenix Mayor Phil Gordon speak about Sky Harbor security concerns Documents obtained by the ABC15 Investigators show they've known for two years that this is going on. In 2005, airport officials hired an outside company to handle security during the times when passenger flights are done for the day. The documents said the guards would not search personal items or the people. Here's the rub: A TSA memo we obtained requires whoever controls airport access to follow federal guidelines that, "provide security against an unauthorized weapon, explosive, or incendiary onto an aircraft." It's tough to prevent that if you're not checking bags. It's even tougher if you're asleep. One on-duty security guard we talked to said it was hard sometimes to keep from falling asleep. In fact, a document we obtained, given to the airport from law enforcement - proves one guard did fall asleep for nearly 20 minutes. Our airport source said it happens a lot. "I've seen security guards fast asleep where they've not even looked up to see somebody walk through the checkpoint," she said. Airport officials told ABC15 that not checking employee bags is a common practice. So why then, when the clock strikes 4:30 a.m. does it all change back? TSA takes over, the X-ray machines are back on, the metal detectors are working, and everyone, including incoming employees just like the ones we watched all night long, are screened. We asked one of the TSA employees that question when we were at Sky Harbor. "We have no control over what the City of Phoenix does," the employee said. So we then asked him if passengers should feel safe. "That's up to the passengers to determine that," he said. The airport employee we talked to said passengers never had a choice in this. "I'm trying to explain how unsafe Sky Harbor Airport is so that you and I and everyone else don't get blown up on a plane that everyone else seems to have access to," she said. Airport security expert Larry Wansley said this needs to be fixed immediately. "You've got all sorts of items that are going into the secure part of an airport unchecked," he said. "I think that presents a very, very dangerous situation that can be exploited that can lead to disaster. That concerns me." Lisa: Are there any reasons that the airport management could give you that could change your mind and make this acceptable?" Larry: "I can't think of any." Lisa: "We're essentially a ticking time bomb?" Larry: "Bingo." http://www.abc15.com/news/local/story.aspx?content_id=568d6b4d-67b7-4116-9098-4c35d8b5ce38#top