Some sub-orbital flights have been undertaken to test spacecraft and launch vehicles later intended for orbital spaceflight.

Since this flight was undertaken in secrecy, it was not public knowledge for many years afterwards.

Numerous pioneering flights were undertaken with the BMW 132.

It was just as clear that the time was past in which an admittedly dangerous but still possible flight into the system of Arkon's white sun could be undertaken.

On 9 September 2011, the first commercial flights were undertaken.

Long flights over water may occasionally be undertaken.

Clinton Administration officials say the flights were undertaken by a Russian airline, not the Russian military, and were motivated by a desire for cash.

The young air force was a small, close-knit organisation comparable to a flying club; however several pioneering flights were undertaken by its members.

With good meteorological predictions, directed Anti-parachute flights might be confidently undertaken, perhaps even on a commercial basis.

"The flight in question on June 25 was not undertaken under U.N. contract and was without the knowledge of the United Nations," he said.