Prayer to Angels

 Rashi (Sanhedrin 44b) A person should always pray that all the heavenly beings strengthen his power of prayer – in other words that the angels should assist him in prayer and that he have no enemies in Heaven

Rashshash (Sanhedrin 44b) The gemora states a person should always pray for mercy that all heavenly beings should strengthen his power of prayer. From this we can bring support for the prayers addressed  to angels which many criticize. However perhaps this is permitted for the individual as is stated in Sotah (33a)

Sotah (33a) A man should never pray for his needs in Aramaic. For R. Johanan declared: If anyone prays for his needs in Aramaic, the Ministering Angels do not pay attention to him, because they do not understand that language!  There is no contradiction, one referring to the prayer of an individual and the other to that of a Congregation.

Shulchan Aruch (OC 

Yerushalmi (Brachos chapter 9:1) If a human is in trouble, he should cry neither to Michael nor to Gabriel, rather he should cry to Me and I shall answer him immediately