X201s, a previous model to the X220 (along with the non "s" X201) has a higher resolution display (1440x900 same res as Mac Air 13) than the X220 (1366x766) and weighs about 1/2 lb less than the X220. Loaded with SSD and 8 GB RAM it is my preference over the X220. If a 12.5" screen vs. the Mac Air 13.3" screen works for needs then you might consider this machine. The Thinkpad Trackpoint is great once you get used to it (probably a few hours/days at most).
For long trips the replaceable batteries of the Thinkpad have an advantage over the Air.
The X201s , X220 are extremely durable machines (I've had Thinkpads since 1999) and have like Apple (and unlike Sony and some others) outstanding warranty service. Thinkpads (on certain models) and Apple both have international warranty.
If you want the larger screen of the Mac Air over the X201s or X220 then I don't see an alternative to the "Air" today.