Sentence one 1. You expect to leave by the or using the noon plane. Sentence two 2. You expect to be in the correct state of mind or in a fresh mind when you leave using the noon plane. Sentence three 3. You are not sure whether you will leave using the noon plane, but its your wish to use the noon plane hope it helped.. .I have explained as per my understanding

1 Hopefully I 'll leave on the noon plane This needs a period. There should be no space after the I and before the 'll It makes sense. It is different because other sentences say someone else is leaving. This one says I will be leaving - and I (the speaker/traveler) want it at a particular time. 2 You ' ll leave on the noon plane in a hopeful frame of mind. again, unneeded spaces around' ll. This one wants the traveler to have a good attitude. 3 You hope you'll leave on the noon plane. This one says the traveler hopes to have a particular flight.