Can you merge sky miles from the different groups?

Don't think so. The idea of seems to be counter intuitive to what the programs are all about, that is customer loyalty to one airline/alliance program or another.

Look at points.com. You can exchange points between programs (with various restrictions) here. I took a look at it once and it wasn't worth it to me, but YMMV.

As far as I know, the Star Alliance group and the One World group are mutually exclusive. You would have done better to choose one or the other to build up your useable miles. We have the Alasa Airlines plan and can accumulate and use our miles on Alaska, American, Delta, British and others. I don't know why you won't fly a 747. Most airlines configure them so ther are 2-seat options at the back three rows. Besides, if you pay for Economy Plus most planes will still be 3X seats on the sides. Apparently Delta has the most effective Econ Plus if you are paying but I don't know what the difference is in miles. Good luck.

The 747s I have wanted to fly on were configured as 3-4-3 but I didn't realize those back rows were just two seats. I have sat in the aisle seat. But you get bumped too much or have to get up for others, that I get no nap/rest that is needed on long hauls. If economy comfort is sold out I'll try to buy/miles for an upgrade or book with another airline. That's why I think I ended up with different alliances. Thanks for the replies and the miles website.

You can use Seatguru for configuration of each type of plane and airline. You will see that at the back of a 747, where the fuselage narrows, the seats are 2-4-2 instead of 3-4-3. Generally there are three rows like this. If you book early enough to have a good choice of seats, you can pick these. KLM/DElta is a good choice.

Short answer: no. Small bunches of miles that are scattered across multiple airline programs are not worth very much, because they generally can not be combined in any reasonable way. A further challenge for you is that Delta, where you say you have the most miles, is famous for making it extremely difficult to book award seats at their "low" level (so people often have to pay double or triple miles for the seat they want). You will need to do some homework. Planning far, far in advance is your best bet.

I have made many trips to Europe with Delta FF miles. My experience with them is if you don't book the day or at the latest, the week after the seats become available (330 days ahead) you will have a hard time getting the low miles seats. The only exception is London, Paris, Rome and Amsterdam which seems to have good low mile availability year-round. Regarding having all your miles merge. I doubt you will be able to do that, but an angle you could pursue is using Air Lingus. If you are booking multiple tickets, you could book one ticket with each of the three groups you have miles with. The only catch is you would need to have enough miles in each group. The final thing to watch out for is expiring miles. Seems like you fly lots of different airlines. Be sure to keep up with when they expire. Delta just switched to no expire dates, but not all airlines are like that. I hope that helps!!

My past trips to Europe have been with Delta, with LH in there to visit son in military. I now know I could have done an Aer Lingus-Delta code share to FRA. Loved Alaska/Horizon airlines, but only flew them as that was best suited for that one travel time just like Hawaiian Air. I'll probably donate some miles to the USO. I have some homework to do on this. I'll start with eliminating one group and work backwards. Thanks everyone for the feedback.