For more comments on the originator Malin Oloier and the technical equipment see case P-iFx3VIiQ0 description page. As I conclude in that case, there is no very compelling reason in the footage to doubt its reliability. However, we can also not fully preclude that this footage is a hoax.
Close-Up View and Smear Effect
The low evening sun over a clear sky causes bright objects to reflect a lot of the sun light into the camera sensor. Therefore, the object appears very clear and bright, which is consistent with the other bright objects in the scene (e.g. the white roof tops and cars).
Similar to other cases of possible WFM footage recorded with the same camera model, the smear effect is noticeable and weak (see figure 1 and case P-iFx3VIiQ0, Close-Up View for the related discussion).
Fig 1. Left: animated close-up. Right: capture from last frame in which it is visible.
The object appears sufficiently large in the footage to observe its shape. Similar to the other case of possible WFM footage from the same originator the object does not seem to have a distinct and stable shape. As Figure 2 shows the object shows a cloud-like morphing behavior. However, the morphing object does not seem to be subject to distortion by drag against the air.
Fig 2. Cloud-like morphing behavior (zoomed version by originator, 2.3MB, 1280 x 1350 pixels))
Travel Path
The originator already provides a detailed analysis of the travel path (figure 3) with which I agree after framy-by-frame analysis.
Similar to another case (h0s_P74oQD4) the object seems to significantly lower its altitude before passing the drone. The object does not follow the parabolic trajectory of a falling object, indicating that it is propelled. After its decrease in altitude early in the footage the object seems to remain on roughly the same altitude.
Fig 3. Traveled path as analysed by the originator.
Estimation of Travel Speed
Employing the standard methodology with an estimated travel distance as shown in figure 4 below, we can infer a travel speed of about 1,638km/h. However, in this case this estimate is particularly unreliable, because the visible travel path in the image indicates a noticeable change of the object's altitude.
However, on the other hand, as figure 1 indicates, a smear effect consistent with such a very fast moving object shot with a Sony Exmor sensor is visible.
Fig 1. Left: animated close-up. Right: capture from last frame in which it is visible.
Fig 3. Traveled path as analysed by the originator.
Fig A.1. Distance between camera and nearest publicly available weather station at Bucharest Baneasa Airport.
Fig 4. Estimated traveled distance (unreliable).