Plane condition is a measure of the everyday wear and tear on your plane. The feature was first introduced in Skyrates 2.5.
Most activities will reduce condition, e.g. trading, fighting manual or auto-resolved combats, taking missions [verify me] and landing/taking off. The rate of reduction is not equal across activities and can be slowed by hiring Mechanics or levels in Perception.
Servicing your plane at the Hangar at any skyland or fuel platform will restore your plane to 100% condition and give you a temporary Lucky Cleaning bonus for every 20% repaired. You will lose one bonus for every 20% condition you lose. Any existing Lucky Cleaning bonuses you have will be removed upon servicing.
To calculate the amount of time your service will take, multiply your plane's tier by 30 minutes and add 30 minutes. For example, a tier 6 Bullfrog's service time would be 6 * 30 + 30, which is 210 minutes or 3 hours and 30 minutes.
Lucky Cleanings are positive modifiers that apply to your plane for every 20% repaired.
SR2.5 had Good Condition in place of Lucky Cleaning. The round also featured Bad Condition, which were negative effects applied for every 20% lost, with an additional 2 applied when reaching 0% and another 3 applied every day thereafter until the plane was serviced.
Given the small difference most effects made, players often only serviced when their influence or mission counts were decreased. This meant that players could end up with a list of bad conditions longer than the client could display.