Those Aircraft Insurance Premiums. What decides how much? First, if you think you are paying too much let your broker do a review of your insurance program. Just fill in the "inquiry form" or complete an Aircraft Application. That said, back to the question. Every aviation insurance underwriter has slightly different guidelines he follows to arrive at a rate but virtually without exception they all take the following into consideration somewhere in their deliberations. Each factor, to the underwriter, represents a change in the chance of an accident or affects his chances of profit from your policy.  Take a look at what you are presenting to the underwriters and compare it with this list. A) What kind of aircraft? Older or rare aircraft do take higher rates. Parts for repair are harder to find and maintenance can be an issue. Some aircraft take higher rates due to known statistical evidence that they have more accidents, are harder to handle or are prone to certain failures. Those homebuilts and ultra-lights are penalized even more. B) Undercarriage? The configuration counts. In order from least costly to most: wheels, skis, floats, amphibians. If wheels are the base then anticipate that floats may take up to a 25% loading and amphibious floats 5 to 10% over that. Taildraggers are often loaded special as well. C) Value? The higher the value then generally the better the rate. In the event of a partial loss to the aircraft more money is available within the insured value to consider repairs instead of a total loss. Because of the higher value you are paying more premium overall and that makes the underwriter feel good. If you insure your aircraft for less then the market value you can suffer in several ways. First, the rate applied to the value may be loaded to adjust for your under-insurance. If there is a serious accident the underwriters can declare a total loss at the lower value you set and then take over the salvage as theirs. This may really make you mad if the aircraft is one you wanted to keep and repair. Sorry. D) Location, location, location? Where you are based and typically operate is a factor. Not only does the location affect the chances of an accident but can have a major bearing on the cost of salvaging the aircraft after an accident and getting to a place for repair. Imagine getting a Bonanza off the North Pole! While there are variations, the general scale from best location to worst is: the southern prairie provinces and southern Ontario; the Maritime's (excluding Newfoundland and Labrador); Quebec; southern British Columbia; Newfoundland and Labrador; most anywhere north of 55º; the high arctic. E) Who are the pilots? This is a big one! The underwriter wants to be confident that you or anyone you are letting fly the aircraft knows how to fly and he asks a lot of questions about this. Generally, the rate is set based on the least experienced pilot you declare even if you say that they are not going to use the aircraft much.  The common factors considered: total first pilot time; time on the make and model; time on the specific aircraft you have; time on the undercarriage declared; advanced endorsements - instrument rating for example; multi-engine time if applicable.     AND the big one - accident record. It has been statistically proven that pilots who have had one accident are more likely to have a second then pilots with no accidents are inclined to have their first one. Violations are considered although minor infractions are rarely given much weight. F) How are you using the aircraft? Corporate business use and just plain mostly for business are considered a better risk than ordinary private use. The business use tends to imply that there is some money available for a higher standard of maintenance and that since customers may be involved, a higher degree of care is exercised. (Maybe, says this writer!) Easier to understand is that uses such as rental of the aircraft and ab initio instruction take much higher rates. Some specialty uses like timber cruising are loaded as well.     The number of hours you anticipate flying each year can be a factor but with a sometimes contrary result. More flying then average can load the rate since the chances of something happening are increased. On the other hand, too little flying may result in a loading if the underwriter does not think you are going to stay fully current. G) Where do you keep the aircraft? There is a lot of argument about this one. Most underwriters prefer a hangared aircraft but what of the World War II wooden hangar where a fire is probable most anytime. Tied down is acceptable but moored which, of course, means a floatplane takes a higher rate. H) Lastly is what side of the bed did the underwriter get out of on the day he is rating your aircraft! At different times companies are more aggressive to put business on the books than at others. Sometimes they are in a mode to increase all their rates if the marketplace competition will let them. It depends so much on what the overall loss record in the country has been and how the particular underwriter has been hit.     AND as the lead in line suggested, the underwriter may be in a good or a bad mood the day your account is presented to him. There is no "rate book" so all the rate setting can be somewhat subjective. Now isn't that sentence a lot of help!