It’s pretty easy to get to Liverpool by airplane, and quite convenient as well!
First of all, the city has its own airport, the John Lennon (what else!) which is located a few km (14) south-east of the city centre (just next to Speke). The runway is just by the river, I find it wonderful to land and see plenty of water below.
It’s a small airport, but surprisingly well connected to the rest of the world. Apart from Ryanair and Easyjet, also KLM flies from here with connections to the US, South America, Africa, Middle and Far East. Being petite, it is also welcoming and has a relaxed atmosphere, usually not much rush or queues too long. If you still want to have a dedicated service at the controls, you can purchase a fast lane ticket that will allow you to join a special queue and be a priority guest of her Majesty. And just for 3 pounds! For personal experience, no point using it, unless you are really in a hurry.
Also, a lovely lady will be happy to provide you with a plastic bag for your liquids if it happened you forgot it.
I always found this airport very comfortable, even when I forgot to get my boarding card and everybody from the staff helped me solve the issue (check-in, controls, gate). Everybody was so helpful that I still had one hour left before boarding.
As for reaching it, its closeness to the city centre allows an incredible variety of choices. You can get a Taxi (less than 15 pounds), your own car, or even the bicycle, because, yes, there is even a bicycle lockers area in the car parking open 24/7. You can leave there your beloved during your travels and get it back when you return. All for just a deposit of 20 pounds (Deposit returned when you give back the locker key).
Or you can choose to go by bus, which is the cheapest way (unless you like cycling). The ticket is 2 pounds and you just have to choose the bus you need. For the city centre, you can jump on the Arriva Airlink 500 (it makes only two stops, for the coach station and Lime Street Rail station) or numbers 80A, 81A, 82A, 86A or N86 for the night bus. These last ones are city buses, there are plenty of stops you can take advantage of, so they can get you very, very close to where you actually need to go). Tickets can be bought onboard and mind that the journey time can vary sensibly depending on the hour (20 min at night up to an hour during peak times) so plan well.
If you want to go by train, the disadvantage is that you can get as far as the Liverpool South Parkway and then you have to get the bus link to the airport. The journey with the bus link is about 10 minutes and it comes almost every 20 minutes.
Hope you will find these info useful. Come back soon to see how else you can get to Liverpool!