οὐκ ἔσθ᾽ ὅπως οὐ, which in grammatical order immediately follows ὡς, can be thus placed because felt as one adverbial expression="assuredly": so often ἔστιν ὅτε (="sometimes"), οὐκ ἔστιν ᾗ ("in no wise"), οὐδεὶς ὅστις οὐ ("everybody"), etc. πτερὸν: no outward sign had been given. The "omen" was in the leading of his will. Cp. the feeling in the Odyssey (more spiritual here than the Iliad) that the gods sometimes act directly on the human mind by inspiring a thought at a crisis. Od. 16.282 (Odysseus to his son, when planning to slay the suitors) “ὁππότε κεν πολύβουλος ἐνὶ φρεσὶ θήσει Ἀθήνη,
νεύσω μέν τοι ἐγὼ κεφαλῇ
”: which anticipates such a πτερόν as is meant here. For πτερόν as=οἰωνός or ὄρνις (= “πάνθ᾽ ὅσαπερ περὶ μαντείας διακρίνει” Aristoph. Av. 719), Schneidewin cp. Callimachus Lav. Pall. 124 “ποίων （“ὀρνίθων”） οὐκ ἀγαθαὶ πτέρυγες”, Propert. 4. 10. 11 “felicibus edita pennis” (with happy auguries).