The engine constantly throttles up and down, not only to counter the drag on the satellite from residual air molecules in near space but also to smooth the flight of the vehicle to minimise the noise in the gravity measurements.

BBC: Goce gravity mapper surfs atmosphere

Your flight has been smooth, the food good, the flight attendants smiling and the seats comfortable.

BBC: Stopover in Abu Dhabi

The early part of the flight was smooth.

BBC: The other pilot

Winds had put Friday's flight in question, and those conditions made for a less-than-smooth ride for the six-person flight crew on NASA's carrier plane.

WSJ: A Shuttle Meets Its City

Flight out of Bozeman was smooth.

FORBES: You Work for Bono!

Five percent pay raises in July for the pilots and machinists, and in October, a richer, ten-year contract for the flight attendants with more coming next year helped United smooth labor relations.

FORBES: Teaching an airline to fly