。
We arrived at Narita a little behind schedule.
Literal
Plan-than a-little behind-[then-て] Narita [at-に] arrive-[past-した].
The te-form 遅れて here is serving as a subordinating conjunction — 'being behind schedule, ...' — chaining the state into the main verb 到着した. This is one of the core uses of the te-form: connecting clauses to express manner, sequence, or background condition. 成田 is of course Narita Airport, Tokyo's main international hub.