Any amendment to a county transportation expenditure plan proposed by the commission is subject to approval by the advisory committee. An amendment which adds or deletes a project, or is of major significance, shall be submitted for approval in the same manner the adopted plan was approved pursuant to Chapter 2 (commencing with Section 131050). Amendments may provide for the use of additional federal, state, and local funds to account for unexpected revenue fluctuations or to take into consideration unforeseen circumstances. Any amendment shall take into account that all appropriate actions shall be taken to give highest priority to the projects in the initial plan, and any amendments shall not delay or delete any project in the initial plan without the approval of the project sponsor.