After Brussels attacks, how safe are U.S. airports ?

WASHINGTON --Added security is coming to U.S. airports in time for the summer travel season. Last month's terrorist bombings at the Brussels airport highlighted vulnerabilities.

The attack occurred in a public area -- before the security checkpoints.

Passengers are likely to see more police in public areas, increased random checks of vehicles and people with larger bags, and additional bomb-sniffing dogs. Twenty-eight K-9 teams have been reassigned from small airports to major transportation hubs.

"I like to think of it as a security environment that you create, that it gets more and more secure as you get closer and closer to the thing you're trying to protect," TSA Administrator Peter Neffinger told CBS News.

That means even after security checkpoints, passengers may be subject to more random checks. Airline cargo and airport employees are also receiving extra scrutiny following the apparent bombing of a Russian jet in Egypt last October.

"There's always a possibility of an inspired individual or a cell that we don't know about to do some harm -- which is why it goes back to then the visible presence and the layers of security, so that you can deter, detect and hopefully disrupt," Neffinger said.

While airline passengers are vetted the moment they purchase a ticket, it's unclear if the Brussels bombers ever planned to go past security.

"It puts it in the category of -- think the Boston Marathon bombers. In a sense, it's in that same category," he said. "It's incumbent upon us at TSA to ensure that we do our best to move people as efficiently as possible into the sterile areas of the airport. "

But all the added security is one factor contributing to long lines at some major U.S. airports.

"I do have concerns about long wait times because it does gather people up," he said. "And in addition to being an inconvenience for the traveler -- which is no small problem -- it does pose a potential challenge with respect to large crowds of people."

Next week, roughly 300 airports submit detailed vulnerability reports to the TSA. The agency plans to create a list of best practices and require them across all the airports.