A hefty chunk of the massive rocket used to deliver the third module of China’s Tiangong space station has fallen back to Earth uncontrolled, triggering the closure of some of Spain’s airspace and leading to hundreds of flight delays. Four days after blasting off from southern China, a large part of the Long March 5B (CZ-5B) rocket broke up as it re-entered the Earth’s atmosphere over the south-central Pacific ocean at 10.01 UTC, according to European and US space authorities. The EU Space Surveillance and Tracking (EUSST) operations centres, which monitored the fragment’s return to Earth, said the core stage of the rocket was about 30 metres long and weighed between 17 and 23 tonnes, making it “one of the largest pieces of debris re-entering in the near past” – and something worth keeping an eye on. Its re-entry led Spain’s air navigation authority, Enaire, to impose restrictions on the airspace over north-eastern parts of the country, including Catalonia and the Balearic islands. In a statement, it said: “Given the uncontrolled entry of remains from the Chinese space object CZ-5B in a descending orbit crossing our national territory, Enaire, in accordance with the recommendations of the European Union Aviation Safety Agency and the inter-ministerial directorates led by the Department of National Security, established an airspace exclusion zone of 100km on either side of the orbit of the space object.” A later update said the closure of airspace, which lasted from 9.37am on Friday until 10.17am, had caused flight delays of half an hour. Spain’s airport operator, Aena, said 300 of the 5,484 flights scheduled across its 46 airports were affected. It was the fourth flight of the Long March 5B since its maiden launch in May 2020. On its first deployment, fragments of the rocket landed on Ivory Coast, damaging several buildings in the west African nation, though no injuries were reported. Debris from the second flight landed harmlessly in the Indian Ocean, while remnants from the third fell into the Sulu Sea in the Philippines. At a regular briefing on Friday, Zhao Lijian, a spokesperson at the Chinese foreign ministry, said the rocket’s re-entry into the atmosphere was a common international practice. “It is understood that [this] type of rocket … uses special technology designed so the vast majority of components … will be destroyed by ablation during re-entry into the atmosphere, and the probability of causing harm to aviation activities and the ground is extremely low,” said Zhao.