Qatar’s Hamad International airport is unlikely to fully open by the end of July, its announced opening date, according to three Doha-based sources close to the project.

The full opening is expected at the end of 2014 at its earliest, though it may host budget flights starting from the end of June this year while the rest of the airport remains under construction.

“It is difficult to estimate exactly when the entire airport will be fully operational. In addition to the infrastructure requirements, safety tests will need to be satisfied in order to get the airport running and if any are failed that could result in further delays,” says a source.

Another source adds that the scope of the project has increased in recent months, requiring additional construction work.

A spokesperson for the airport’s steering committee denies its full opening will be delayed. “The airport will partially open to low cost carrier and cargo operations in the coming months before fully opening by the end of the second quarter of this year. We are still determining the exact dates.”

The opening of the $17.5bn airport, previously known as New Doha International, has been met with significant delays after initially aiming for a 2008 launch.

“They may have been able to meet earlier deadlines if they had chosen to scale down the scope and launch it in stages,” says a source.

An ongoing legal battle with the German/UAE joint venture firm Lindner Depa Interiors contributed to the delays. The company issued a lawsuit against the airport in September 2013 after its contract for the construction of 19 lounges was pulled.

The new airport is seen as a crucial project marking one of Qatar’s first megaprojects while the country ramps up its infrastructure capacity. The country’s grand ambitions are estimated to lead to $165bn in project spending over the next four years.

Once the airport opens, national carrier Qatar Airways will be moving its full operations there, with other airlines set to follow. It has not yet determined the exact number of airlines that will be operating from it, its spokesperson says.

The airport will initially cater to 30 million passengers a year, a 30.4 per cent on Doha International’s capacity of 23 million.