AS World Cup fever builds across the globe, Brazil's airlines have announced they will put on almost 2000 additional flights to cater for the hordes of football fans set to travel around the country.

The flights - to be mainly operated by the nation's four main carriers, TAM, Gol, Avianca and Azul - will help connect the 12 host cities, which are spread across the vast South American nation.

These include cities where the Socceroos will play their group games.

But if you haven't booked your flights to Brazil yet, then you may be out of luck.

Flights during the period on the fastest route to Rio de Janeiro from Australia (Qantas and LAN via Santiago) have either sold out or are close to double the normal flight price.

Fans booking flights from Melbourne can forget about any dates on Qantas and LAN from June 4 through to June 23. They are booked solid. June 25 to 28 has also sold out.

On Emirates, the cheapest return flights to Rio available last week from Sydney and Melbourne cost more than $4000 for an economy seat via Singapore and Dubai. Travellers on those flights would face up to 38 hours travel time.

And return flights via the US - either Los Angeles and Houston or Dallas and Miami - to Rio would set travellers back more than $6000.

Within Brazil, the country's largest airline, TAM, will put on 1000 additional domestic flights, while smaller carriers Avianca and Azul will cap one-way fares at $US425 during the World Cup.

"We made a large request for additional flights to meet passenger demand based on the geographic distribution of host cities and match dates," TAM Airlines chief executive Claudia Sender said.

"In addition to transporting passengers within Brazil, TAM will reinforce its operation to bring international tourists by requesting an additional more than 200 international flights into the country during the period."

As an example of the increased services, TAM flights to Rio de Janeiro are expected to increase from 100 to 112 per day, while the number of flights to the capital, Brasilia, will grow from 83 to 96 per day.

There will be an additional five daily TAM flights to the Amazon jungle city of Manaus, bringing the total number to 18.

There will also be an additional six daily flights to Cuiaba - where the Socceroos play their opening match against Chile on June 13 - on top of the existing five.

The 2014 World Cup begins June 12, 2014 in Sao Paulo and will finish on July 13, 2014, with the final to be played at the Maracana Stadium in Rio de Janeiro.

- with AAP