Where are the tickets?

A husband and wife bound for a holiday in Majorca were waiting patiently in the airport lounge. Suddenly, the husband said.
'You know, darling. I wish I 'd brought the piano with us.'
'Don't be ridiculous!' exclaimed his wife. 'Why on earth should we have brought the piano?'
'Because I've left our tickets on top of it. ' replied the husband.