The 23-year-old suspect, identified only as Ilia S., spent hours at one of the eateries at Warsaw's Chopin airport on December 26, which raised the suspicions of security officers.
He was detained and a court ruled that he be arrested for a month.
The Ukrainian had on him a device for radio jamming, designed for frequencies reserved for aviation communications and navigation, investigators said.
A spokesman for Warsaw prosecutors told reporters the Ukrainian had made extensive testimony, but did not answer the key questions.
The man said the device found on him was legal.
Prosecutors are checking how he entered Poland. The suspect said he had previously visited Dubai, Canada, Greece and Italy.
Prosecutors had requested a three-month arrest, but the court ruled one month would be enough to appoint an electronics expert, Polish state news agency PAP reported.
The expert is expected to help ascertain what is recorded on the confiscated devices and what exactly is their function, reporters were told.
The man pleaded not guilty to charges of breaking aviation law by attempting to interfere with wireless communications systems. He faces up to five years in prison if convicted.
(pm/gs)
Source: polskieradio24.pl, PAP