Oregon is not too big on trip permits as we are known as the tree hugger state. I'm not sure how it works though if your license is from out of state. If you pre-purchase would it be better to get a trip permit from your state before you board the plane?
https://www.oregon.gov/ODOT/DMV/pages/fees/vehicle.aspx#trippermits
Buy a Trip Permit
You can buy trip permits at your local DMV office or by mail. You can also buy Heavy Motor Vehicle, Heavy Trailer, and Registration Weight trip permits at most Motor Carrier Transportation Division (MCTD) registration offices.
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To apply for a trip permit, provide:
Your name and address;
Your driver license or ID card number and the state which issued it;*
The year, make, and model of the vehicle;
The vehicle identification number (VIN);
If Oregon DMV has no record of the vehicle, provide a copy of your insurance card or policy, registration card, sales contract, or a pencil tracing of the VIN.
Insurance company name and policy number (for motor vehicles only);
Any additional requirements listed in the section for the type of trip permit you are applying for; and
Trip permit fee:
By mail: Check or money order to "DMV."
DMV office: Pay by cash, credit or debit card, or check or money order made out to “DMV”.*
Out-of-State Trip Permit
You can drive in Oregon using your valid trip permit from another state. You must keep proof of insurance in the vehicle.