once+past perfect

[allthewayanime]

Which one is correct to use with 'once'?

Once they had finished ,they were ready to continue.
or

Once they finished they were able to continue.

 

[5jj]

Both are possible.

 

[allthewayanime]

So 'once' can be used with both past simple and past perfect without any difference?

 

[5jj]

1a. Once they had finished, they were able to continue.
1b. Once they finished, they were able to continue.

2a. Once they had finished, they were ready to continue.
2b. Once they finished, they were ready to continue.

There is no real difference between the meaning of 1a and that of 1b.
There is no real difference between the meaning of 2a and that of 2b.