The Aër (Greek: Ἀήρ, lit. the "air"; modern Greek: Αέρας; Slavonic: Воздухъ, Vózdukh) is the largest and outermost of the veils covering the Chalice and Diskos in the Eastern Orthodox Church and the Byzantine Rite Eastern Catholic Churches. It is rectangular in shape and corresponds to the veil used to cover the chalice and paten in the Latin Rite, but is slightly larger. It is often made of the same material and color as the vestments of the officiating priest, and often has a fringe going all the way around its edge. Tassels may also be sewn at each of the corners.
It takes its name either from the lightness of the material of which it is made, or from the fact that during the Nicene Creed in the Divine Liturgy, the priest holds it high in the air and waves it slowly over the Chalice. Its original use was to cover the Chalice and prevent anything from falling into it before the consecration. It symbolizes the swaddling clothes with which Christ was wrapped at his Nativity, and also the grave clothes in which he was wrapped at his burial (both themes are found in the text of the Liturgy of Preparation).
The Aër is first mentioned by name in an explanation of the Divine Liturgy by a writer of the sixth century, and is also alluded to as "the so-called Aër" in the Acts of the Council of Constantinople.
At the Great Entrance (when the sacred vessels are brought in procession to the Altar), the priest will place the Aër over the deacon's left shoulder before he hands him the Diskos (the priest himself will carry the Chalice). For this reason, the Aër will often have ribbons sewn onto it, so it can be tied securely in place. If there is no deacon serving, the priest will place the Aër around his own neck like a cape, which will leave his hands free to take both the Diskos and the Chalice.
Just before the chanting of the Symbol of the Faith (Nicene Creed), the Priest will kiss the Diskos and Chalice (by kissing the Aër in the place where it touches each vessel) and the front edge of the Holy Table (Altar). During the Creed, the priest will hold the Aër above the Gifts and waive them slowly, indicating the activity of the Holy Spirit. When a bishop is serving the Liturgy, the concelebrating priests will hold the Aër during the Creed as the bishop kneels (or bows his head) underneath it. After the Creed, the Aër is folded and placed on the Holy Table.
At the Ordination of a priest, when it is time for the Great Entrance, the Bishop will drape the Aër over the candidate's head and shoulders, and in this manner he will carry it in the procession. The candidate will not enter the Sanctuary with the rest of the clergy, but will remain standing at the Holy Doors. The Bishop will remove the Aër from his head and place it over the Gifts and cense them, after which the Ordination takes place.
During Feasts of the Cross a cross is laid on a tray covered by an Aër and decorated with basil leaves and flowers, and carried by the priest from the Prothesis to the Holy Table. During the course of the service, this tray will be placed in the center of the church and all the faithful will come forward to venerate the cross.
At the death of a priest or bishop, when his body is vested for burial, his face will be covered with an Aër to show his closeness to the Sacred Mysteries.