Airplane departures and arrival stats

Given that a flight departs (on-time) = P(d)=.83, and arrives (on-time) = P(a)=.82...and prob that it departs & arrives on time is .78:

1. what is the prob. that an aircraft will arrive on time or depart on time?

- ???

2. Are these events (a,d) independent?

- I said they are dependent upon eachother...but mabe I misintrepreted this....- the latter would only be correct if it was the same plane so what is correct?

3. If after a couple of years P(a)=.9 & p(d)=.85 and P(a and d)=.77 are we able to say that these events are mutually exclusive? or independent? Why or why not?

- I said they are mutually exclusive because they cannot occur at same time...but again is my interpretation wrong...we may not be talking about the same aircraft here. How should this be handled?