All Daniel Stenberg wanted to do was endure about fifteen hours of air travel from Sweden so he could spend a fun week talking code at Mozilla's all-hands meeting in San Francisco. But the Moz developer and maker of the Curl data transfer tool was denied boarding in Stockholm, en route to London and then The City By The Bay.

Of course, he tweeted the news.

That took an unexpected turn. I'm denied entry by ESTA out of the blue. So... no trip for me I suppose 😕 — Daniel Stenberg (@bagder) June 26, 2017

Going back home. To cry. To curse. To write code from home instead. Fricking miserable morning. No #sfallhands for me. — Daniel Stenberg (@bagder) June 26, 2017

“ESTA” is the Electronic System for Travel Authorization and is a pre-screening program for citizens of nations that don't need a visa to visit the United States. Securing an ESTA authorization takes a few minutes on a dedicated web site and costs US$4 to apply and then a further $10 if approved, whereupon the US Department of Homeland Security lets your airline know it's okay for you to board.

Stenberg jumped through those hoops and was apparently approved for an ESTA, but was informed that something was awry as he tried to board his British Airways plane in Stockholm.

Just what went wrong isn't known, but frequent travelers of El Reg's acquaintance tell us that sometimes ESTA information doesn't flow smoothly from Uncle Sam to airlines. If an ESTA record provided to a carrier isn't completely clear, they deny boarding because the consequences of carrying an unapproved passenger are significant.

Whatever the reason for Stenberg's denied boarding, he was vexed. But others were angry as they saw this week's partial reinstatement of President Trump's travel ban behind the denial of boarding, and therefore possibly a sign of a crackdown on techies visiting America. Silicon Valley hates that idea as it relies on talent from around the world to swell its ranks, or just come and talk to colleagues in multinational companies.

The good news is that a Mozilla spokesperson has knocked the It-was-The-Donald-wot-done-it theory on the head, in the following statement sent to The Register:

We are focused on providing support for our employees and we're looking into ways to resolve and understand the circumstances. Currently, we do not believe the situation is related to the US Administration's proposed travel ban or the recent Supreme Court ruling.

And the bad? Trump's promised "extreme vetting" process is nowhere to be seen, despite promises it would be an early priority for his administration.

At least Stenberg wasn't forced to take a computer science quiz at the US border. ®