Latvian authorities are hunting a 26kg (57lb) drone that went missing mid-flight, causing air-traffic problems.
The aviation authority has restricted flights below 19,500ft (6,000m) in the region while they search for it.
While officials say it is likely the drone, which took off on Saturday, has landed, it had enough fuel to fly until 19:10 local time on Tuesday (17:10 BST).
Many members of the public reported sightings but none has been confirmed.
The non-military drone is understood to belong to a local unmanned aerial vehicle (UAV) manufacturer.
During a test flight, the company lost communications with the drone and lost track of its location, Latvian media reports.
About 3.5m long and 5.5m wide, with an airspeed of up to 70km/h (43mph), it was last seen flying at about 200m.
On Monday evening, the aviation authority said the possibility the drone was no longer in the air was becoming increasingly likely but multiple planes were still searching.
Despite lower air traffic across Europe due to the coronavirus pandemic, the errant UAV has caused some problems, closing airspace over Riga International Airport and causing the redirection of a flight from China to Tallinn.