ISLAMABAD (Reuters) - Pakistani Prime Minister Shahid Khaqan Abbasi on Tuesday inaugurated the long-delayed new airport in the capital, Islamabad, replacing the cramped Benazir Bhutto airport often criticized by travelers.

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A Pakistan International Airlines pilot waved a green and white Pakistani flag out of his cockpit window after landing the carrier’s first commercial flight at the New International Islamabad Airport.

With a sleek glass-front entrance, spacious check-in areas and jetway bridges for boarding, the Y-shaped airport promises an end to the congestion that has frustrated air travel in the past.

“This airport rightly reflects what has happened in Pakistan in the last five years,” said Abbasi.

Abbasi’s ruling Pakistan Muslim League-Nawaz (PML-N) party had been eager to open the new airport before national polls, likely in July, as it touts big-ticket infrastructure as sign of economic progress in the South Asian nation of 208 million people.

Abbasi’s government is spending billions of dollars on upgrading Pakistan’s transport infrastructure and ending energy blackouts, with freshly paved motorways as well as dams and power plants popping up across the country.

Abbasi, who has a pilot’s license and is a founder of a Pakistani budget airline, said new airports in the cities of Multan, Faisalabad, Quetta and Peshawar were in the final stages.

The new Islamabad airport, which has the capacity to handle 15 million passengers annually and space for further expansion, was first suggested in the 1980s and has been more than a decade in the making.

The delays have become a running joke with many Pakistanis, who mock the frequent announcements that the new airport would open soon and subsequent clarifications of further delays. The airport’s most recent delay was last month.

“Nothing is impossible but this project definitely seemed impossible,” quipped Abbasi, in reference to his government inheriting the project in 2013.

The new airport is about 15 km (nine miles) from the capital. Benazir Bhutto airport was in the nearby city of Rawalpindi and attached to a military base.

International travelers often complained about chaotic scenes at the airport and in 2014 it was voted the worst in the world by the “Guide to Sleeping in Airports” website, prompting widespread criticism of the airport in Pakistani media.

The new airport is due to start full operation on Thursday.

(This story fixes tense to “happened” in paragraph four.)