Would you pay more for extra airport security?

An officer from the Transportation Security Administration checks travel documents for passengers traveling through Reagan National Airport.
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Deadly terror attacks in Brussels on Tuesday have sparked calls for expanded security in the crowded areas around airports in the U.S., protecting human lives at any cost.

While it's impossible to truly value safety, does the U.S need to spend to expand airport security to the level of other countries? How much would it cost and who would pay for it?

In some countries, like Israel and Turkey, transportation to and from airports faces similar scrutiny to boarding areas. But in most U.S. airports, security starts well inside airports, leaving trains, shuttles, lobbies and parking lots less secure, experts said.

"Of course, in Israel, per passenger they spend about 10 times as much as we spend here in the U.S. Per passenger," John Pistole, Anderson University president and former TSA Administrator and FBI deputy director, told CNBC's "Squawk Alley" on Wednesday. "So the question is, who pays for it? Is it passenger fees? Is it funded government mandates?"

Passenger fees have been used to ramp up security after past terror incidents. The Passenger Fee, also known as the September 11 Security Fee, is now $5.60 per one-way trip and $11.20 round-trip, the TSA website said. Carriers also paid a set of Sept. 11 security fees until 2014.

The 10-to-1 figure referenced by Pistole has been bandied about since 2010, when outlets such as the The Washington Post compared spending by El Al, Israel's national carrier, to TSA spending, finding that El Al spent $56.75 per passenger while the TSA spent $6.93.

Metro-North Railroad police officers patrol Grand Central Terminal, in New York, Tuesday, March 22, 2016.
New York tightens security after Brussels bombings
Members of the New York National Guard patrol New York's Penn Station on March 22, 2016.
Why still terror risk, after all that security money spent?

The U.S. serves more than 894.24 million passengers with a total TSA budget of $7.44 billion, working out to $8.32 per flier. El Al serves about 2.2 million passengers per year, a financial release showed, with 2014 security screenings priced at $130.96 million, coming to $59.53 per passenger. It's not 10 to 1, but certainly upwards of seven times more.

But that back-of-the-envelope figure has some limitations: It uses just one national carrier traveling to Israel, and uses the total TSA budget (including non-screening costs) and the total number of U.S. passengers (including connecting flights that don't require screening). Plus, there's the apples-to-oranges scale: El Al serves about the number of customers a year that TSA screens per day.

The TSA is slated to spend $2.974 billion on just on security screenings for more than 708 million passengers this year, working out to at least $4.20 per customer.

El Al Israel did not immediately respond to requests for comment.

Military police patrol the Brussels Airport on November 18, 2015 in Zaventem, eastern Brussels. Belgium's national security level has been raised to three, following a series of coordinated attacks by Islamic State jihadists in Paris on November 13, 2015.
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It's also important to note that more spending isn't necessarily better. Despite the $900 million spent on TSA observational screenings between 2007 and 2013, "human ability to accurately identify deceptive behavior based on behavioral indicators is the same as or slightly better than chance," the Government Accountability Office found in a 2013 report.

Still, TSA's Peter Neffenger has studied the Israeli system, including their behavioral detection techniques, he said during congressional hearings this month.

"In fact, the Israelis have come back and given us some advice," Neffenger said. "We've also tried to validate that. In fact, we've recently sent a report to Congress, which I think does validate the science behind the behavioral indicators. It's not a 100 percent program, it's not intended to be; it's an indicator. You look for certain types of behaviors."