Washington: US President Barack Obama has weighed in on the issue of increased airport screening, a topic rattling the nerves of air travellers as the United States enters the busiest travel season of the year.
Tightened security measures include the use of so-called "naked" scanners that take full-body X-ray images that show passengers` genitals.
Transportation Security Administration (TSA) agents manually pat down passengers who refuse to be screened by the devices.
The TSA says the scanners protect fliers following the foiled 2009 Christmas Day plot to down a US jet by a Nigerian traveller who concealed explosives in his underwear.
Critics say the devices and the pat-downs are invasive and demeaning.
Obama, speaking to reporters in Lisbon following a summit with NATO allies and European Union partners, said he "understand people`s frustrations" over the measures.
He said that following the attempted Christmas bombing, "TSA personnel are, properly, under enormous pressure to make sure that you don`t have somebody slipping on a plane with some sort of explosive device on their persons."
Since the explosive on Nigerian "underwear bomber" Umar Farouk Abdulmutallab "was not detected by ordinary metal detectors, it has meant that TSA has had to try to adapt to make sure that passengers on planes are safe."
"Now, that`s a tough situation," said Obama.
"One of the most frustrating aspects of this fight against terrorism is that it has created a whole security apparatus around us that causes huge inconvenience for all of us. And I understand people`s frustrations."
He said he has asked the TSA to "constantly refine and measure whether what we`re doing is the only way to assure the American people`s safety."
But TSA and US counter-terrorism experts say that the procedures are the only ones they believe are "effective against the kind of threat that we saw in the Christmas Day bombing”.
Obama vowed to "constantly" ask his counter-terrorism team whether what they are doing is "absolutely" necessary, or if there were other ways to meet the same objectives.
He, however, said he had a "confession" to make.
"I don`t go through security checks to get on planes these days, so I haven`t personally experienced some of the procedures that have been put in place by TSA," he told reporters.