After people suspected of being Islamic terrorists carried out attacks in New York, New Jersey and Minnesota in recent weeks, Donald Trump said law-enforcement agencies should consider turning to profiling as part of their counterterrorism plans. His comments were widely interpreted to mean the singling out of Muslims, though Trump denied that was his intent. The Republican presidential nominee held up Israel as a possible model; he said that the country’s use of profiling has been successful and that Israelis “aren’t complaining about it.” (Trump made similar comments after a man who pledged allegiance to the Islamic State fatally shot 49 people at an Orlando nightclub in June.)

Trump is far from the first American political figure to call for adoption of Israel-style security methods. But security experts say it’s not clear how important ethnic or religious profiling is to the success of Israeli security. And even many experts who support profiling in Israel say that it would be much harder to apply successfully in the U.S., where terrorist attacks haven’t followed consistent patterns. Also, contrary to what Trump said, some Israelis are complaining about profiling there: Civil rights groups have done so, and their protests have helped lead to changes in security practices.

The U.S. faces different security challenges than does Israel, which is under threat from terrorists who have emerged from the country’s Arab minority and from Jewish and Palestinian extremist groups. But one important situation in which the two countries face relatively similar threats is aviation.

There hasn’t been a successful hijacking of an Israeli plane since 1968, and there hasn’t been a successful attack on civil aviation in Israel since a 1972 shooting killed 26 people at the country’s international airport. Experts attribute that success at least in part to tight security procedures, which they say include profiling of passengers. (Like most security agencies, the Israel Airports Authority doesn’t share details of its practices, lest that information be used against the agency by people intent on overcoming its defenses.) But some security experts who have observed Israel’s system cite factors other than profiling as more important. In particular, they say interviewers and observers at Ben-Gurion International Airport run drills daily, to prepare for every kind of security threat. They also have extensive behavioral science training, looking for signs of threats in how passengers react to questions.

“They have mastered the art of reading body language, reading eye movements,” said Daniel Wagner, managing director of risk solutions at the security company Risk Cooperative in Washington, D.C.

The U.S. has taken a different approach to aviation security. The Transportation Security Administration, which oversees U.S. airport security, is exempt from federal guidelines barring racial profiling, but the practice is forbidden at the agency. TSA spokesperson Mike England said the agency has concluded that beyond any legal or ethical issues, profiling doesn’t work.

“Profiling is not tolerated at TSA,” England said in an email. “TSA has long made it clear that profiling is not only discriminatory; it is also an ineffective way to identify someone intent on doing harm.” (The TSA is being investigated by the Homeland Security Department’s inspector general after a TSA employee alleged that Somali Americans were being profiled in its Minneapolis office; the TSA has also said it is looking into the claim.)

The debate over profiling goes beyond aviation. Security experts distinguish profiling in general — which is based on behavior that’s been displayed by terrorists in the past — from demographics-based profiling and say that the former is inescapable in security. “The concept of profiling, in its root form, is using past information to predict future performance,” said Sheldon Jacobson, who is a professor of computer science at the University of Illinois at Urbana-Champaign and has researched aviation security.

When looking for known suspects such as the Boston Marathon bombers, there’s no real controversy about using race or ethnicity as a descriptor. What’s contentious is the idea of targeting a whole group of people for additional scrutiny based on how they look: not just millions of Muslim and Arab Americans but millions of other Americans who might look to a security officer like they could be Muslim or Arab — because, after all, there’s no way to tell what religion or ethnicity someone is just by looking at them.

Experts disagree about the usefulness of this kind of profiling. David Harris, who is a professor of law at the University of Pittsburgh and wrote a book about racial profiling, said that focusing on superficial attributes such as a person’s skin color could make security agents less focused on the person’s behavior and therefore worse at perceiving real threats. “There is no evidence that exists anywhere that using this actually makes your security or policing any better,” Harris said. “There are plenty of reasons to think it makes your efforts less effective.”

Even if it were to increase the chance that a search or interrogation targets someone who poses a threat, profiling could be a net negative for security efforts. Repeatedly being singled out for more extensive checks could discourage people from coming forward with the kind of intelligence that first brought the suspect in this month’s New York City bombing to the attention of authorities, years before the attack.

Corey Saylor, a spokesperson for the Council on American-Islamic Relations, said antagonizing potential sources doesn’t make sense. “Why again do you want to apply a broad brush and vilify a bunch of law-abiding people when you already have a community that has a good reputation for self-reporting?” Saylor asked.

In Israel, no consensus exists on the value of profiling based on demographics alone. Airport screeners do profile in disproportionately targeting Muslims and Arabs for the most extensive questioning and baggage check, but security experts said that if screening decisions were to become too predictable, terrorist groups would recruit people from outside the profiled groups. (Many attempted terrorist attacks on Israeli air travel were carried out by people who weren’t Arabs or Muslims. And Jewish terrorism also is an increasing threat in Israel, usually against Muslims.)

A 2008 survey of air passengers in Israel highlighted how profiling can alienate the people being profiled. Just 62 percent of Israeli Arab respondents said they were treated fairly in their security check, compared with 96 percent of Israeli Jewish passengers. And Israeli Arabs’ suitcases were opened for additional checks at a rate nearly five times higher than Israeli Jews’. “We could clearly see that there are strict security measures that were applied toward Arab passengers that weren’t applied to Jewish passengers,” said Badi Hasisi, director of the Institute of Criminology at Hebrew University and co-author of a study based on the survey.

After legal and activist challenges to the practice, the Israeli Airports Authority in 2014 stopped opening people’s luggage in the main terminal area, in front of other passengers. Raghad Jaraisy, head of the Arab rights unit at The Association for Civil Rights in Israel, said the change meant that passengers no longer have their belongings exposed and no longer are stigmatized before fellow passengers as security threats. “That makes the whole security process much less humiliating for Arabs,” Jaraisy said. (The civil rights association and other groups continue to push for ending profiling based on ethnicity in security screening.)

But what if we knew that ethnic profiling worked in Israel and we set aside the political, legal and ethical concerns to ask whether it could work in the U.S.? Even some security experts who advocate its use in Israel are doubtful. “It’s not something where you decide tomorrow morning, we will do what Israel does,” said Rafi Sela, CEO of the Israeli security consulting company AR Challenges. “It doesn’t work.”

Data on the recent history of terrorist attacks shows how much more concentrated the threat is among a few groups in Israel than in the U.S. According to the Global Terrorism Database, there were 201 deadly terrorist attacks in Israel between 1996 and 2015 that had a known primary perpetrator group, and 79 percent were committed by just four groups (Hamas, Al Aqsa Martyrs’ Brigade, Palestinian Islamic Jihad and Hezbollah). Just 2 percent were committed by unaffiliated terrorists. Over the same time period in the U.S., there were 58 deadly attacks for which the primary perpetrator was known, and 78 percent were committed by unaffiliated terrorists.

So-called lone-wolf terrorism accounts for the majority of recent U.S. attacks, and many of the attackers had no known formal ties to terrorist groups before their attack. They also had a wide range of stated motives. “The variability of the lone wolf is so high at this point,” Jacobson said. “The noise is overwhelming the signal right now.”

The scale of security needed in Israel is also much more limited. For example, the U.S. has more than 100 times the number of air passengers as Israel does. “It would be impossible to scale what they’re doing,” Jacobson said.

Also, Israel has a workforce full of military veterans, thanks to the country’s mandatory military service, including some with training in interrogation or security. Sela said it would take a huge effort for the U.S. to institute the kind of training that would be required to fulfill Trump’s vision of putting in place Israel-style security. “The problem is, he has no clue how expensive this is,” Sela said.