Is the following scenario classified as curtailment or a plan amendment?

Bobby's Paper Airplane Company's wants to eliminate the single-employer defined benefit pension plan by eliminating the future earning of pension benefits for 85 percent of its employees (i.e., freeze its pension plan). If they decide to freeze its current pension plan for 85 percent of its workforce, it will not offer any new pension benefits to its affected employees through another plan. The current pension plan is the only retirement benefit arrangement it provides to its affected employees. The plan's pension benefits are based on years of service and average salary for the last five years of the employee's service period. Employee paid on hourly or salaried, who have attained six months of service are participants in the pension plan.

Under the plan freeze, Bobby's will eliminate the accrual of additional pension benefits for future service, while NOT taking future salary increases into account in computing the average salary for the last five years before retirement when determining the pension benefits earned for service before the plan freeze. The pension plan freeze, if adopted, will be effective on November 1, the beginning of Bobby's next fiscal year, and is expected to be approved and communicated to affected employees before October 30 year-end.

My confusion: I could classify this as a curtailment and a plan amendment, but am not sure which one this leans more towards. Cutting 85% of all employees future benefits including increases, sounds like a curtailment based on the definition from the FASB. It also sounds like a normal plan amendment change. They are simply not going to take into account future salary raises in the 5 year average. So which is it? I can seem to make the argument for both sides but dont believe it qualifies for both sides.