CARACAS, Venezuela – Come to Venezuela and you might get a longer trip than you bargained for.

The U.S. Embassy in Caracas issued an advisory Tuesday urging Americans to be careful when travelling to Venezuela because of the steep drop in airline service to the South American country.

The number of seats on flights between Venezuela and the U.S. has fallen by more than half since the beginning of the year, according to the Venezuela Airlines Association. The three largest U.S. carriers – Delta, American and United Airlines – all slashed their service to Venezuela this summer.

The cause: A dispute over some $4 billion in cash trapped in the socialist country.

Decade-old currency controls mean that airlines need government approval to convert local earnings into dollars. And the socialist government, running low on dollars itself, has been preventing carriers from repatriating revenue, with some airlines waiting over a year.

Each successive reduction in service has left passengers scrambling to rebook seats, often for significantly more than they first paid. The scarcity of flights has sent airfares soaring; a one-way ticket to New York now costs more than $1,000.

On Tuesday, the Embassy urged U.S. travellers to leave themselves enough time to make alternative arrangements should their return flights vanish.

While most carriers have reduced service, some, including Air Canada and Italy’s Alitalia, have left Venezuela altogether.

Diminishing access to the global air traffic network has many middle class Venezuelans grumbling that they are trapped in their own country.

Even Venezuela’s top soccer club is suffering. It said last week it could not find a flight to an international tournament in Peru and would have to spend several days travelling to Colombia and catching a flight from there.

President Nicolas Maduro has downplayed the airline exodus, dismissing it as a crisis cooked up by the “bourgeois press.” At one point, he said carriers were only temporarily adjusting schedules to meet demand for flights to Brazil for the World Cup.

He has warned that airlines abandoning the country wouldn’t be allowed to return.