请问订的机票的行程上出现莫名信息. 第一次见, 求教~~~

之前通过I fly china的一家旅行公司定了一张回国的机票. 上去一个查行程的网站(www.virtuallythere.com), 上面出现如下信息.

For at least one of your flights, you must change the aircraft en route even though your ticket may show only one flight number and have only one flight coupon for that flight. Further, in the case of some travel, one of your flights may not be identified at the airport by the number of your ticket, or it may be identified by other flight numbers in addition to the one on your ticket. At your request, the seller of this ticket will give you details of your change or aircraft, such as where it will occur and what aircraft types are involved.

有谁见过这个吗? 能不能告诉我这个是不是正常? 我需不需要去担心? 谢谢啦!!!