Do all international airports have special security screening for US-bound flights?

I remember being at Warsaw Chopin in 2010 and witnessing a queue of Poles flying to Chicago.

Since we were in the regular transfer area (EU-non EU) I suspect they did not have to pass any additional screenings.

They still had to produce some kind of aďditional paperwork at the gate, or so it seemed.

Certain world airports have "Pre-clearance". This means there is a section of the airport that is cordoned off and inside the USA as far as immigration and customs are concerned. To get to the gate, you must clear US immigration and customs. But hey - no second Customs when you arrive.

Airlines that do not fly out of Pre-clearance gates will operate their own company immigration document check at boarding. This is required by law and the airline is fined very heavily if they bring someone to the country whose papers were not in order. You can't escape this, except at Pre-clearance airports.

Some non-pre-clearance international areas of airports destined for the USA will have additional security checks.

Some airports do not have airside passageways between all their many terminals, so arrivals needing to change terminals may need to exit and re-clear security. Often, so do international arrivals. This tends to happen to very successful old, but built-up airports like Detroit and LAX, you can't easily bulldoze the existing terminals and there isn't room on the property for a new "everything terminal".

Very small airports that fly the rubber-band airplanes (like Goose Bay, Scapa Flow or Lukla) will not be up to full "sterile area" standards, and their passengers will need to go through security again.

This all varies from route to route, so you have to check for each case.

My understanding is that you're asking about the additional security checks within the airside, when you get to the boarding gate.

I believe this is up to the airline and depends on location.

The only two airports where I have not encountered these checks were:

• TLV - everyone goes through them, so no need to single out US-bound flights
• PEK - Given the absolute surveillance state that is PRC, interviewing passengers at the gate is probably redundant.

Other than that, I've encountered varying degrees of extra security for US-bound flights in any other airport I've been to.

I've been flying internationally with United in the last several years and they had them everywhere (mostly in Europe). I flew with British Airways from LHR once, and they just had a documents check and a quick in-person assessment (I didn't see anyone being taken aside for further interview). Swiss in ZRH also had a full blown security check for US-bound flights at the gate when I flew with them a couple of years ago (I believe they shared infrastructure with United for these checks).

Just to clarify, these are not "TSA-equivalent" checks. In fact, TSA checks are pretty ineffective, when it comes to human factor, since there's no interviewing or profiling involved (or even allowed). There were some changes suggested by GAO in 2019, but given the political climate in the US they can only go so far.

Personal opinion below (although I've seen no evidence otherwise and quite a lot of evidence to support this opinion):

While these checks are annoying, they're extremely effective. During the mid-20th century there's been a lot of incidents of plane hijackings and bombs on board (e.g.: the PanAm incident), and these checks were designed to prevent the recurrence of such (e.g.: The El Al incident).

The fact that planes' hijackings are rare nowadays goes to show that these checks work, both in prevention and deteral. If 9/11 has taught us anything is that given the opportunity someone will take it.

For those readers who hadn't lived during the 70s and 80s of the last century, a more recent reminder of why these checks are important would be the "underwear bomber". The perpetrator boarded a US-bound flight in Amsterdam, passing all the post-9/11 security measures, and successfully bringing an explosive device on-board. This happened in 2009, and it is due to this incident that the US-bound flights now receive a bit extra security.

US flights are not the only ones, similar checks are routine for decades for all the flights to Israel (and from Israel), and for the same reason.

The airlines are held responsible for the passengers they bring into the US, and they are reluctant to believe that the local airport security checks are up to the TSA required checks in every detail; they do not however have supervisory input or any control on them, so they need to make their own.

My tip is to not fly from Munich; they are by far the worst and most annoying.

Not all airports have extra-secure areas for U.S.-bound flights, and even then, this is only relevant if you get the dreaded "SSSS" on your boarding pass. All other times, the screening isn't particularly stringent.

Some airports will shove U.S. flights to the furthest corner of the terminal, de facto separating them from all other traffic. Madrid–Barajas does this, where all non-Iberia U.S.-bound flights depart from the A gates at Terminal 1, which can be up to 15 minutes away from the security line. I've gone through SSSS screening here once and it was tucked away at a faraway corner of the departure lounge, occupying a not-insignificant amount of space.

Other airports will keep their U.S.-bound flights mixed in with other traffic, but will have a designated part of the gate for SSSS screening. When I flew from Sydney back to LA in 2019, I was also subject to SSSS screening and it was in an enclosed part of the gate area.

Finally, some airports will have a second security check for U.S.-bound flights in addition to the first level of security screening after immigration, which is separate from SSSS screening. Manila does this, where all U.S. traffic goes through two layers of security, and in fact this is the most stringent screening for U.S. flights I've seen.