You will need
To change the tickets on the plane, contact your airline's ticket office or on the website where you booked the ticket to clarify the possibility to cancel the trip and get some of the money spent on the ticket. If you want to cancel, but to postpone the trip, find out whether you can do it and whether you are assigned some extra charge from the airline. If you are unable to use the tickets and the scheduled date of the trip due to airlines, we are entitled to a full refund of the ticket, and, in some cases, additional compensation of moral or material injury (in the presence of justification).
Otherwise, the change of tickets depends on what rate you chose during the purchase. For example, the price of the excursion allows you to change any ticket, even very close to the departure date, special rates, including discounts, on special terms, on "hot" lines practically do not allow this possibility. Some tariff provides for the change of ticket, but with mandatory deduction of funds from the cost of the ticket as a penalty. Sometimes you can change your rate, as some transport companies offer the ability to change tickets for other modes of transport or Vice versa.
If the tickets were not used, and the travel date has passed, such a case is considered individually. If there are valid reasons and documents supporting them (illness, refusal in issue of visa, etc.), in some cases it is possible to obtain a fraction of the price of the unused ticket back.
The sooner you decide to change the plane tickets, the easier and faster it will be possible to implement. In the early stages simply cancel the booking for the aircraft, but instead to reserve more tickets.
Especially to quickly and conveniently change the ticket on the plane if you have booked via relevant online services.