The plane reached the bottom of the slope with barely enough momentum to clear the ramp.
Water landing, thought Artemis. Death by ducks.
Then something occurred. A boost of power came from somewhere. It was as if a giant forefinger had flicked the plane forward into the air. The tail rose, and Artemis fought the pedals to keep it down.
How is this happening? Artemis wondered, staring befuddled at the controls, until Holly punched his shoulder for the second time in as many minutes.
“Air start!” she yelled.
Artemis sat bolt upright. Air start! Of course.
The solar plane had a small engine to get the craft off the ground, and after that the solar panels kicked in; but without a battery the engine could not even turn over, unless Artemis hit the throttle at the right time, before the plane began to lose momentum. This might buy them enough time to catch a thermal for a couple of hundred feet, enough to clear the lake and outfly the arrows.
Artemis waited until he sensed the plane was at the apex of its rise, then opened the throttle wide.
Artemis pumped the throttle for a second time, and the plane’s engine caught. The single nose propeller chugged, jerked, then spun faster and faster until its blades formed a continuous transparent circle.
“What happened?” Artemis wondered aloud. “What was that noise?”
“Wonder later,” said Holly, “and fly the plane now.”

The Last Guardian, Chapter 16