After a storm, a cruise ship was wrecked on the sea. An emergency rescue ship immediately departed from the port to the accident site. The accident site was 840 kilometers away from the port, and the speed of the rescue ship was 20 kilometers per hour. A small plane was parked on the deck of the ship. The plane took off a few kilometers away from the destination and flew towards the accident site at a speed of 220 kilometers per hour. If the pilot spent 22 hours on the road from the time the ship left the port to the time the plane arrived at its destination, how many hours did the plane spend in the air?
一场风暴过后，海面上有一只游船遇难了．一艘紧急救援船立即从港口出发，前往出事地点．出事地点距离港口840千米，救援船的速度是每小时20千米．船的甲板上停着一架小型飞机．在离目的地还有若干千米飞机起飞，以每小时220千米的速度向出事地点飞去．如果从船离开港口算起，到飞机到达目的地，飞行员在路上用了22小时，那么飞机在空中飞行了多少小时．
<gadget id="calculator">22 * 20</gadget>
<output>440</output>

<gadget id="calculator">840 - 440</gadget>
<output>400</output>

<gadget id="calculator">220 - 20</gadget>
<output>200</output>

<gadget id="calculator">400 / 200</gadget>
<output>2</output>

<result>2</result>