出発 and 到着: departure and arrival
Distinguish departure and destination, and schedules from completed events.
Leaving the starting point
出発 (しゅっぱつ) means leaving for a destination. 「九時に駅を出発しました」 says that the speaker departed from the station at nine.
In 「東京へ出発します」, 東京へ is the destination. 「東京を出発します」 means leaving Tokyo; the particle changes the direction even with the same place name.
Reaching the destination
到着 (とうちゃく) means arriving at a destination. 「十時に空港に到着しました」 says that the speaker arrived at the airport at ten.
「到着したら連絡します」 means getting in touch upon arrival. It announces an action after a condition, not an already completed arrival.
Scheduled versus actual
「到着予定は午後三時です」 gives a scheduled arrival of three in the afternoon. 予定 marks a planned or expected time, not confirmation of actual arrival.
「出発は遅れましたが、予定どおり到着しました」 means departure was late but arrival was on schedule. A delay at one stage does not automatically carry over to the next.
Does 「まだ出発していません」 mean the speaker has already reached the destination?
Show the answer and why
No. It means departure has not yet occurred, not that arrival is complete.