On May 17, two female passengers boarded their flight in Makassar in South Sulawesi, Indonesia, bound for Manado, North Sulawesi. Soon after, they told flight attendants they had bombs in their checked luggage. They didn’t.

On the same day, on a flight carrying 147 passengers out of Ternate, North Maluku, to Jakarta, a man told flight attendants that he, too, had a bomb in his checked bag. He didn’t.

A few days later, on a flight out of Banyuwangi in East Java, two of the city’s councillors were questioned by police after they told their Garuda flight attendants that perfume in their carry-on was actually an explosive device. It wasn’t.

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After a series of suicide attacks in Indonesia last month, the bomb hoaxes have added a new headache for travellers just as the airline industry enjoys something of a renaissance. Safety and on-time departures now rival foreign carriers. A suite of shiny new terminals, including one opening this week in Semarang that is nine times bigger than the one it is replacing, make travel bearable.

For aviation specialist Gerry Soejatman, who counted 10 bomb hoaxes on aircraft last month, the false alarms are something of an own-goal for an industry that has battled back from the brink.

“This just reminds people of the bad old days when, really, the industry has moved on,” Soejatman said.

The rash of hoaxes comes at an unfortunate time – just as an estimated 20 million Indonesians leave the cities for their hometowns to celebrate the end of the Muslim holy month of Ramadan, an otherwise ideal opportunity to showcase the facilities at new airport terminals in Semarang, Central Java and West Java.

At Ahmad Yani Airport in Semarang, an airy US$160 million terminal will help deal with an overflow of passengers. The previous terminal was designed for no more than 800,000 passengers, yet serviced more than 4 million last year.

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“It’s very important to bring in tourists,” says Hidya Ramadhina, a spokeswoman with state-owned Angkasa Pura 1, which operates the airport.

Even here, bomb threats are all too common. Last month the city had two: one in the centre of town and one at the airport, which temporarily shut the old terminal down. The hoax, spread by social media, alleged that a box found at the terminal contained explosives. Instead, it contained escalator parts.

“We don’t have any plans to pursue charges,” Ramadhina says.

That is not uncommon. Unlike other jurisdictions where authorities can come down hard on bomb threats, Indonesia takes a light touch, usually letting perpetrators off with a warning.

That’s a far cry from Singapore’s reaction in April, when fighter jets were scrambled to escort a Thailand-bound plane back to the city state after a passenger claimed to have a bomb.

Patience in Indonesia, though, may finally be running short. Late last month, university students aboard a Lion Air flight from Pontianak, West Kalimantan, triggered panic when before take-off they told a flight attendant their laptop computers contained bombs. Hysterical passengers overpowered the flight crew, ripped open emergency exits and poured onto the wings, even as the engines were still running. Distressing images of passengers sliding down the engine casings onto the tarmac several metres below were beamed onto television news programmes and social media.

This time the students were taken into custody.

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“We hope that this legal action will be a deterrent,” Indonesia’s transport minister Budi Karya Sumadi, told local media. “This needs to be a lesson for all of us that we can no longer joke about bombs.”

Soejatman says Indonesian culture has struggled to adjust to the rigid protocols of air travel, and travellers are not always that savvy. “Society needs time to catch up,” he says.

But the cavalier attitude may also reflect ambivalence towards terrorism among some, says Muhammad Heychael, a media researcher with the non-profit group Remotivi.

“There’s a big part of society that thinks news about terrorism is itself a hoax or overstated or even a conspiracy against Islam,” Heychael says. “We still don’t have a cultural strategy when it comes to confronting radicalism.”

Most of Indonesia’s population of 260 million are tolerant. Nevertheless, a 2016 survey conducted by the Wahid Foundation think tank in Jakarta found nearly 8 per cent of respondents claimed to harbour radical religious views. Of the 1,520 surveyed, seven individuals said they had carried out a violent act against a minority.

Even so, Indonesia’s aviation sector has improved greatly in recent years.

In 2016 US authorities cleared Indonesian airlines to fly in American airspace again after a nine-year ban that followed a string of accidents.

Indonesian carriers are more reliable, too. Five carriers, including Garuda Indonesia, have an on-time arrival rate of 85 per cent or better, edging US carriers, which had on-time arrival rates of no more than 84 per cent last year, according to US government data.

And when delayed, passengers can wait in nicer surroundings. Last month, the US$150 million Kertajadi International Airport, which can accommodate 5 million passengers, opened 200km from Jakarta. And after a two-year transition, Jakarta’s US$500 million Terminal 3 is set to handle all international flights in time for the Asian Games in August.

By law, bomb threats that result in injuries or property loss can carry an eight-year sentence. But other than the pair in West Kalimantan, it’s unclear whether any other pranksters will face legal action. National police spokesman Muhammad Iqbal didn’t respond to repeated requests for comment.

“We think hoaxers should be charged seriously to teach them a lesson,” says Yado Yarismano, spokesman at state-owned Angkasa Pura II, which manages western airports including Jakarta’s Soekarno-Hatta.

Yarismano declined to say whether he felt the police response was adequate.

“These incidents are very disruptive. They hurt passengers and they hurt the airlines.”