electric

One of the innovations at this year's Paris Olympics was supposed to be an electric flying taxi service.

Lilium's aircraft uses 30 electric jets that can be tilted in unison to swing between vertical lift and forward flight.

In May one of its key partners, the engineering giant Rolls Royce pulled out of a deal to supply electric motors for the aircraft.

Given all the uncertainty and expense, you might wonder why investors put money into new electric aircraft in the first place.

"It was an electric night," said Andres White Correal, a jewellery specialist from Sotheby's, adding the unnamed female buyer was "ecstatic".