plural or singular

[Allen165]

"The company operates in the fields of upkeep, repair, and maintenance of aircraft."

Would it be better to write "in the field of"? Can one construe "upkeep, repair, and maintenance" as one field?

Thanks!

[SoothingDave]

It sounds like three words for the same thing to me. Maintenance says enough. He is involved in the field of aircraft maintenance.

[Allen165]

It sounds like three words for the same thing to me. Maintenance says enough. He is involved in the field of aircraft maintenance.

Unfortunately, I have to use all three. Would you use "field" or "fields" in this case?

Thanks.

[SoothingDave]

I would use "field."