Spot error in these sentence:
1)All the former classmates are planning on attending the formal reunion ceremony

My book says "we don't plan on doing sth, we plan to do it". But Oxford dictionary says:
plan (on sth / on doing sth) to intend or expect to do sth:
[v] We hadn’t planned on going anywhere this evening. Ç [v to inf] They plan to arrive some time after three. Ç [vn] We’re planning a trip to France in the spring—are you interested?
I don't see anything grammatically wrong with are planning on attending.
Stylistically, however, I wouldn't put two -ings so close together, so I'd change are planning to plan.
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But plan on +V-ing is the pattern. If you want V-ng, you always get two in this pattern, but if you don't, you wont receive anything. How can we change this double V-ing like you say:I wouldn't put two -ings so close together ?
.... are planning to attend ...." sounds more correct !
Hi dear.......

I think "planning to attend" is much better than "planning on attending"
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