Yes, you can decrypt wep using airdecap-ng from aircrack-ng suite, or using wireshark gui. However you can also use tshark to decrypt wep with known key, and you can define many keys to be used to decrypt wep packets as well.
Quick example -
shell>tshark -t ad -o 'wlan.enable_decryption:TRUE' \
-o "wlan.wep_key1:1122aabbcc" -nr wlan-wep.pcap
By the way, you can also decrypt wpa similarly.