Good day, DorothyMae,
Regarding Revelation, it is the context that determines whether or not something is being spoken of literally or symbolically. So to determine what these things are we must look at the overall details.
First of all, in the first verse John sees what he calls a star falling from heaven to the earth, then in the same verse it states that the star was given a key to the Abyss. So right away we can determine that this is not a literal star. Then in verse 2 the star is referred to as a "he." Also, if we look at Rev.12, stars are used symbolically to represent Satan's angels. The conclusion then, is that that this star who is given the key to the Abyss is an angel.
Secondly, this star/angel is opening the Abyss, which is an opening into the earth. In further support of this, when he opens the Abyss smoke like a gigantic furnace billows out, obscuring the sun and the sky.
Thirdly, out of the smoke from the Abyss comes what John calls locusts. However, the fact that they are described as having hair like women's hair, teeth like lions teeth, faces resembling human faces, breastplates of iron, tails and stingers like that of a scorpion and the fact that it is said that they have a ruler over them which is the angel of the Abyss, then it quickly becomes apparent that these are not your garden variety locusts, but are demonic beings being let out of the Abyss. These combined details should dissuade anyone from interpreting these locusts as being helicopters or some other kind of military vehicles.
Based on all of the provided information in the context , what John is describing should be interpreted in the literal sense, recognizing these as demonic entities that humans have just never seen.