This airport doesn't have as many flights as New Chitose Airport, so at first there weren't any planes visible from the observation deck.
Literal
This airport [topic-は] New-Chitose Airport [comparison-ほど] flight-count [subject-が] not-many [reason-ので], observation-deck [from-から] looking even, first planes [subject-が] did-not-exist [polite-past-でした].
The negative comparative ~ほど~ない ('not as much as X') is the standard structure for 'less than.' 新千歳空港 is New Chitose Airport, the main airport serving Sapporo in Hokkaido. 送迎デッキ ('observation deck,' literally 'seeing-off and welcome deck') is a compound common at airports and train stations. The から見ても adds 'even looking from.' 飛行機がいません uses いる for aircraft — interesting, as planes are inanimate but treated as animate here (perhaps personified, or perhaps the passengers/pilot make it animate).