How do you make grammatical sense of 飞架 in the expression 港珠澳大桥飞架三地? Is it "the Hong Kong-Zhuhai-Macao Bridge flies a three-city frame"? Or "the Hong Kong-Zhuhai-Macao Bridge: flying and supporting three cities"? Or something else?
You could easily understand 飞架 as (to) span.
ABC’s definition of 飞架 is as follows:
arch/span high over (e.g., of a great bridge)
Pleco C-E’s definition is fairly similar and they add the example sentence:
Yī qiáo fēijià nán-běi, tiānqiàn biàntōng tú. (Máo Zédōng)
A bridge will fly to span the north and south, | Turning a deep chasm into a thoroughfare.
Looking at your original question we could come up with something like:
飞架三地 = spans over three cities
If you want to take a leaf out of Pleco’s book you could render it as:
flys to span over three cities
but that doesn’t sound nearly as natural.
If the sentence was "港珠澳大桥高架三地", we can understand "高架" means "rise high"
Imagine the bridge was like a dragon, and this dragon flying high above the sea through three territories
港珠澳大桥飞架三地 would mean "the Hong Kong-Zhuhai-Macao Bridge rises high above the sea like dragon fly through three territories"
飞架 would mean "rises high and extends far"
飞架三地 would mean "rises high and extends across three territories"
simply "fly across" -- describe the bridge as a metaphorical dragon