Cornwall faces losing £1bn of spending by visitors over 14 months because of coronavirus, tourism bosses say.
Visit Cornwall head Malcolm Bell said the projected loss, estimated for March 2020 to April 2021, would have a "major impact on business viability".
Mr Bell said he wanted to urge potential visitors to make bookings to offer hope for the tourism industry.
He and companies said customers could be confident they could get money back or postpone if Covid caused problems.
The £1bn figure - a decrease of about 45%, Mr Bell said - was also raised by the Cornwall Local Enterprise Partnership (LEP) in a Cornwall Council briefing on Wednesday.
LEP chairman Mark Dudderidge said the amount was being lost to the county despite "a busy summer".
Mr Bell said tourism businesses were having a cash-flow crisis, and that, although the medium and long-term outlook was good because of vaccines, they needed to get through the coming months.
He said: "We're certainly 100% behind the lockdown. But I don't think it's irresponsible to look ahead for the summer and the autumn and say: 'Book now,' so that businesses have got some healthy reservations already in."
Leanne Locke, regional manager for Lovat Parks in Cornwall, which runs three sites, said bookings could be changed.
She said people needed something to look forward to and to see "a happier time awaits and we'd like to give hope to people that that will happen".