Altaria locations — where to catch

In Lumiose City (Legends: Z-A)

• Magenta Sector 4 — Static Encounter
• Wild Zone 18 — Walk
• Wild Zone 20 — Walk

In Paldea (Scarlet & Violet)

• Casseroya Lake — Walk
• Dalizapa Passage — Walk
• Glaseado Mountain — Walk
• North Province (Area One) — Walk
• North Province (Area Three) — Walk
• North Province (Area Two) — Walk
• Socarrat Trail — Walk
• South Province (Area Four) — Walk
• South Province (Area Six) — Walk
• Tagtree Thicket — Walk
• West Province (Area Three) — Walk, Static Encounter
• West Province (Area Two) — Walk

In Blueberry Academy (Scarlet & Violet – The Indigo Disk)

• Canyon Biome — Walk

In Hoenn (Ruby, Sapphire & Emerald)

• Sky Pillar — Walk

Other games (6)

• Sword / Shield — The Isle of Armor (Gen 8): Ballimere Lake, Dyna Tree Hill, Frigid Sea, Frostpoint Field, Giant's Bed, Giant's Foot, Max Lair, Path to the Peak, Slippery Slope
• Ultra Sun / Ultra Moon (Gen 7): Ultra Space Wilds
• X / Y (Gen 6): Kalos Route 21
• Black 2 / White 2 (Gen 5): Abundant Shrine, Nature Sanctuary, Unova Route 14, Unova Victory Road 2
• Black / White (Gen 5): Unova Route 14
• XD (Gen 3): Citadark Isle

Altaria — full Pokédex entry