Riding on the backs of human beings and riding (also) on his beautiful car Pushpaka. Indra also with the celestials went riding on his elephant Airavata,
आस्थाय रुचिरं याति पुष्पकं नरवाहनः। ऐरावतं समास्थाय शक्रश्चापि सुरैः सह॥