Is this question grammatically correct in regards to the word "hangared" pertaining to aircraft.
If your aircraft is hangared in another locality, please let us know immediately.
This is the first time I've seen hangar used as a verb and most online dictionaries I checked only list it as a noun. Nevertheless, verbification is a common enough process in English and when a noun is converted to a verb, it follows normal conventions.
The standard way of building the past tense is indeed adding the ending -ed so yes, if you are using hangar as a verb, hangared will be its simple past and past participle. It is equivalent to peak and peaked for example.
Searching google for "define hangar" does return a definition listing it as a verb and even uses this example sentence: "the army choppers that were hangared out at Springs", so you are not alone. It just does not give a source for the definition and the three or four other dictionaries I checked do not list it as a verb.
So, yes, the sentence (which is not a question but a request) you posted is OK with respect to hangared though the usage will probably be strange to people who are not accustomed to talking about aircraft. Since it is unlikely that the request will be addressed to people who are not in the field, it will probably be readily understood by its target audience.
That is almost certainly a sign or note at an airport. In such cases (signs and notes), certain liberties can be taken.
To a pilot, the note would be perfectly clear.