They're American carriers, no doubt about it, Yorktown class.
4 seconds sound clip from the Midway (1976) movie soundboard.
You can hear this line at 01:42:27.817 in the Blu-ray version of the movie.
Quote context
[...]
- Sacrifice themselves like samurai, these Americans.
- They're off now, wave-hopping after the survivors.
- We have no fighter umbrella over us?
- No, sir. We're trying to recall them, get them back up to the patrol altitude.
- How many fighters are standing by to cover our attack against the American carrier?
- Barely enough to do the job, sir.
- They're American carriers, no doubt about it, Yorktown class.
- Get through to Nagumo's flagship. Be quick about it!
- The transmitter isn't working, sir. We're not sending out any signal!
(WW2 Airplanes - Bombing Squadron) (2)
- What's that look like to you down there?
- A Jap destroyer! Going someplace in one hell of a hurry.
[...]