Your sentences do not contain a 'future perfect' form. 'Will' often expresses the speaker's certainty about something.
1. Luke's plane took off two hours ago, so he will be in London by now.
2. Luke's plane took off three hours ago, so he will have landed by now.
In #1, the certainty is about Luke's present location; In #2, it is about something that has happened. There is no future involved.