I am travelling using United Airlines and I booked flights for myself and a relative, and wanted to ensure we were both physically sitting on the same plane. I checked the flight codes upon booking but realised afterwards that the flight codes were slightly different: mine was UA 179 K whereas my relative's was UA 179 W. The flight codes are the same (UA 179) but the classes are diifferent (K and W). Will this still mean that we will both be sitting on the same plane? (I have checked other details such as departure time, layover times, aircraft... and they're all pretty much the same). Many thanks.
Yes, you will be on the same plane (and in the same section, namely, economy.) As Berwyn mentioned, these are just different fare classes, both of which are economy fares. The K fare is a cheaper fare class than the W fare.
What appears to have happened is that there were no more seats available in the cheaper K fare class when you booked the ticket for your relative, so their ticket ended up in the somewhat more expensive W fare class. In general, this just means that you paid more for your relative's ticket than for your own. There are a few more small differences, but they probably don't apply to your situation (these are mostly just related to things like upgrade eligibility/priority for people who have elite status with the airline.)
In general, as long as you're on the same flight number on the same date with the same origin city, you are booked on the same plane, regardless of what fare class you have booked (or what class of service you have booked.)
United airlines booking classes can be seen here.
- K Deep Discount Coach
- W Discount Coach
These are different fares within the coach/economy section.