The fields within the travel authorization are available to edit up until a travel reimbursement is initiated. After that point, no changes may be made.
Blanket travel authorizations cannot be updated after a travel reimbursement has been entered against it.
Please keep in mind that the travel authorization is an estimate of expenses. While there are special authorizations that need to occur prior to travel, such as the use of rental vehicles, use of personal vehicles, and overnight lodging, the final reconciliation will occur when the travel reimbursement is processed.