By Crispian Balmer and Emily Rose

JERUSALEM (Reuters) -Woken by air raid sirens, hurrying to bomb shelters, scouring travel sites for escape routes — thousands of tourists in Israel have found their holiday plans upended by the country's conflict with Iran.

Israel launched a surprise attack on Iran in the early hours of Friday, shutting down the national airspace and telling people to remain where they were as the arch Middle East foes traded deadly blows.

The violence has left around 40,000 tourists blocked in Israel, according to the Ministry of Tourism. Airlines are cancelling flights until further notice, leaving travellers to decide whether to wait it out or seek costly detours through neighbouring countries.

Justin Joyner, from California, is on holiday in Jerusalem with his father John, who lives in Nevada, and his son. They had expected some possible disruption, with Israel locked in a months-long conflict against Hamas militants in the Gaza Strip.

But, like most locals, they did not foresee a whole new war.

"We didn't expect Israel to attack Iran. That is a completely different level of escalation," Joyner said from his hotel in East Jerusalem, which, for the past two nights, has seen Iranian ballistic missiles flash overhead like a rain of meteorites.

"It's unsettling to feel the shockwaves of intercepted missiles above you, and to take your family down to a bomb shelter. That's just something we don't think about in America," he said.

Dr. Greer Glazer, who lives in Cleveland and was in Jerusalem for a nursing training program, faces a race down 10 flights of stairs in her hotel to reach the shelter when sirens sound -- as they have done regularly since Friday night.

"I feel safe," she said, "but waking from a dead sleep and running to the safe room, that's been the hardest. My family is scared to death ... They think it's 24/7 destruction, but it's not like that."

THE JORDAN ROUTE

Glazer had been due to return home on June 29, but is looking to bring forward her departure. The easiest exit route is via land crossings into neighbouring Jordan and then a flight out of Amman airport which has been operating in daylight hours.

Israeli media reported that the transgender U.S. influencer Caitlyn Jenner, who only flew into Israel on Thursday for Tel Aviv's since-canceled Gay Pride Parade, had left through Jordan.

Hours earlier, she had been photographed drinking a glass of red wine in a bomb shelter. "What an incredible way it has been to celebrate Shabbat," she wrote on X.

Not everyone is rushing to leave.

Karen Tuhrim is visiting from London to see her daughter, who lives in Tel Aviv. "Within two days of being here, Israel attacked Iran. So now I'm stuck," she said.

Unlike Jerusalem, Tel Aviv has taken direct hits from the Iranian missiles and Tuhrim has had to dip in and out of her hotel's shelter. But she said she felt safe and was happy to be near her daughter.

"For me, personally, at the moment, I feel better being here than in London, watching it all on the news, knowing my daughter is here. So, for now, we're good."

Israel's Ministry of Tourism has set up a round-the-clock virtual help desk in English and Hebrew for stranded travellers.

But for anyone stuck here, all the museums are closed until further notice, entrance to the Old City of Jerusalem is barred to non-residents and many shops remain shuttered.

"The streets and shops are empty," said Jerusalem resident Anwar Abu Lafi, who saw no quick end to the gloom.

"People are yearning for a break, to find something good in this existing darkness. We are deluding ourselves into thinking that the future will be better," he said.

(Additional reporting by Steven Scheer and Sinan Abu Mayzer in Jerusalem, and Artorn Pookasook in Tel Aviv; editing by Sophie Walker)