The main danger in a light aircraft is that the spray accidentally discharges in the cabin. That could temporarily blind and incapacitate the pilot, which would obviously be extremely dangerous.
According to an article from the Alaska Department of Fish and Game, GA operators typically take special precautions when transporting bear spray:
You can take bear spray, but you must tell the carrier and the pilot must know. It requires special handling. Carl Ramseth is with Alaska Seaplanes, a Southeast Alaska regional service, which has planes on both floats and wheels. Bear spray is defined as a hazardous material, he said.
“You can fly with it, but it needs to be declared,” he said. “We ask passengers as they check in – people on scheduled flights as well as people going to remote locations. People don’t realize it could be a problem, so we always ask. There is paperwork filled out. We transport it in a sealed can, stored in a part of the aircraft that is not in the main cabin, so there is no risk of it going off in the cabin. Or it goes in the float compartment of a float plane.”
Some carriers use a length of heavy duty black PVC sewer pipe, four inches in diameter and threaded with caps at both ends. Several cans can be stacked and sealed in the tube for transport.
Another article on the same site says that some operators don't want to carry it at all:
“Bear spray is a big one, it’s dangerous,” said Stewart of Skagway Air. “We can do it, but we really prefer not to. Typically speaking, most carriers won’t allow it. You don’t want that going off in an aircraft.”
“We really try to have them leave it behind,” said Vanessa Thompson, with 40-mile Air.
Even if you don't have a floatplane, as long as you have some duct tape it's still possible to carry the spray outside the cabin:
ilya_ktsn, CC BY 2.0, via Wikimedia Commons
It might look odd, but it's allowed by the FAA per JO 8400.34 - Fixed-Wing External Loads in Alaska:
Items in this group are small, lightweight, and temporarily attached with bungee cords, straps, ropes, etc. Below is a list of items that are examples that may be carried under a Standard Airworthiness Certificate. For the purpose of this order, these temporarily-attached items are not considered design changes or alterations.
[...]
Cans of animal repellent, such as bear spray or pepper spray.
US federal law prohibits carrying of any type of chemical weapon on commercial aircraft, in federal buildings, prisons, and courts. According to TSA, bear pepper spray is a forbidden item to bring with you on a plane. Instead, TSA suggests purchasing it at your destination ( check the prices here ) and leaving it behind when your trip is over. There is also one more option, you can rent it.
Is Bear Spray Allowed In Checked Luggage?
Why you shouldn’t carry bear spray while flying?
If a self-defense spray weighs less than four ounces it can be checked on commercial aircraft. Since a standard bear spray weighs around 7.9 ounces, this means it doesn’t meet this requirement.
Since extreme temperatures and pressure can alter the bear spray’s performance, you must know how to store it carefully. Both extremes either hot or cold can affect the efficacy of spray.
Even storing in a hot car may cause its contents to explode. On the contrary, bear spray will still be effective at temperature below freezing. In addition, some bear sprays tend to be extremely flammable. If something goes wrong a bear spray could cause serious troubles.Therefore, bear sprays can never be carried in airplane, not in checked or carry-on baggage.
What about other aerosol sprays?
Is it allowed to carry a perfume in your carry on baggage? You will be surprised to know just how many everyday household things are not allowed on the plane! This is why it never hurts to check the guidelines to ensure that you are not carrying anything that is on the restricted list.
One such common household item that you might not think twice when putting in your luggage is aerosol. Whether it be hairspray, perfumes, a body mist or a shaving cream, all of them come under aerosol toiletry. But, the question arises, are you allowed to carry such times in checked baggage?
Any aerosol that is categorized as toiletries are allowed in carry-on and checked baggage, as long as they comply with the quantity restrictions.
In carry-on luggage, such items are subjected to the 3-1-1 rule. This means that you can carry them in your carry-bag as long as they are in don’t weigh more than 3.4 ounces each. You can’t bring more aerosol based toiletries than what can be fitted in a 1-quart sealed transparent plastic bag.
When it comes to checked baggage, you can carry full-size aerosols without any issue. There is no restriction on the size and quantity of the aerosol containers in your checked baggage.
Read commercial airline policies
Don’t fly with dangerous outdoor gear that can complicate air travel. Keep a bear spray with you while recreating. Be vigilant. If you live outside of US, look at commercial airline policies before traveling. Learn to handle bear spray with care. It could be a life saver spray when used correctly.