General liability is not enough on its own
A standard commercial general liability policy is written for ordinary business risk. Working on and around aircraft is not ordinary business risk, and general liability policies frequently carry aviation exclusions that render them close to useless at exactly the moment you would need them.
What to look for instead
Aviation-specific coverage appropriate to work performed on client aircraft. The important question is not the headline limit — it is whether the policy explicitly contemplates work on aircraft, and what the exclusions say. A large limit on a policy that excludes aviation is a large number that does nothing.
Ask for the certificate directly
A certificate of insurance should come to your risk or procurement contact from the vendor, naming the coverage in force and its dates. A vendor who is reluctant, or who sends a screenshot rather than a certificate, has told you something.
Questions worth asking
Does the policy cover work performed on the aircraft itself, or only third-party bodily injury and property damage? What are the aviation exclusions? Is coverage current, and when does it renew? Can the certificate name us as required by our own procedures?
Where we stand
We carry aviation-specific coverage appropriate to working on and around client aircraft, and we provide a certificate on request directly to whoever needs it. Ask and it goes out the same day.