You may be required 'Prior Approval', or may need 'Advance Expense (cash prepayment)', or the company may arrange certain type of tickets ... The proceeding is troublesome than anything. If you try to extend the schedule as personal trip, you will totally not understand what you should submit.
On the other hand, your Boss or Accounting personnel who receive the "Business Trip Application" won't be so happy. It will be hard enough only to check expenses and detailed travel plan. The words of "travel plan" are already nonsense because anyone can change their reservation at anytime, anyplace. Also in Expense Settlement processing, there no longer is a necessity for advance cash because most of the purchase can be paid with 'Company credit card'. If you need a settlement, you'll claim it in Travel Expense Report of afterward.
In the Workflow below, it is focused on 'abolishing Advance cash', and on giving Prior Approval on [Overview of Travel].
What is excellent on this workflow is, destinations of the travel plan (place name) that entered can be referred in Google Maps. Because "travel route" and "travel cost" can be understood with one click, "person who gives approval (the Boss)" or "person who does audit" can understand the business trip summary instantly.
[Business Trip Approval flow]