Parashat Bo

When Moshe Rabbeinu warned the Mitzrim about the upcoming Makkat Bechorot, he was vague about the exact time it would come, as it says:
(שמות פרק יא' פסוק ד') "וַיֹּאמֶר מֹשֶׁה כֹּה אָמַר ה' כַּחֲצֹת הַלַּיְלָה אֲנִי יוֹצֵא בְּתוֹךְ מִצְרָיִם"
And Moshe said, “around midnight...”
Rashi explains that the reason why Moshe did not specify exactly midnight is that the Egyptian astrologers might err and discredit Moshe by saying it was not really midnight when Makkat Bechorot happened.
:This is the quote of Rashi
"...שאמר משה כחצות, דמשמע סמוך לו או לפניו או לאחריו, ולא אמר בחצות, שמא יטעו אצטגניני פרעה ויאמרו, משה בדאי הוא".
…that Moshe said ‘around midnight’ (כַּחֲצוֹת), which implies close to it, either slightly before or slightly after, and he did not say ‘at midnight’ (בַּחֲצוֹת), lest Pharaoh’s astrologers err and say, Moshe is a liar.
The question is that we find later in the parshah that when describing Makkat Bechorot, it says, “and I will pass through Mitzrayim,” and Rashi explains, “like a king who passes from place to place, and in one instant they are all struck”.
So, is it not a contradiction that on one side we say that they were killed instantly, while on the other hand it is described as Hashem passing through, which suggests that they were killed at different points in time?
Also, why was Moshe so concerned that the astrologers would say that he lied and that Makkat Bechorot was not at midnight, when there would be no way for them to prove it, so their claim anyway would not be credible?

Hint to the answer: What halachic considerations would one need to have in mind when traveling on a plane and wanting to daven Minchah with regard to shekiah?

We know that the time of sunset in Bnei Brak is not the same as the time in Tzfat. Why? Because the time of sunset depends on a city’s location relative to the sun, and therefore it changes from place to place. The sun “sets” according to the horizon of that specific location.
Therefore, regarding sunset when a person is on an airplane, it may be flying over an area where sunset will be, for example, in three hours, and ten minutes later, the sunset will move forward thirty minutes, and so on. So, for example, if one is on a flight from Europe to Eretz Yisrael, the time of sunset will constantly move forward.
Therefore, one must clarify how the time of sunset is determined on an airplane. The same question can be asked regarding a fast day. At what point during the flight may one break the fast, since the time of night is constantly changing?
Similarly, in Dubai there is a very tall building, the Burj Khalifa, which is almost a kilometer high. They say that one can see the sunset twice the same day, if after sunset below, one goes up in the elevator and would be able to see the sunset again.
The question is, if one is at the top floor of the Burj Khalifa, according to which sunset would it be considered shekiah?

Morenu HaGaon Rav Amrom Fried shlit”a writes:
We always judge a person according to his current location. Therefore, when one is traveling on an airplane, we look at the airspace beneath the plane to determine whether it is night or day, and according to that we calculate the times of night and day and shekiah.
As a result, a person who is traveling on a fast day from one place to another, depending on the country from which he is traveling, may sometimes need to fast for thirty hours, and sometimes only for eighteen hours.
Same too at the Burj khalifah we would calculate shekiah according to the ground level.
According to the above, we can now understand the answer to the week’s question given by the Maharil Diskin. He explains that since Egypt is such a large country, the exact time of chatzot would be different in each area, and so Hashem would kill the firstborn at the exact time of chatzot in each place.
This answers the first question, that it is not a contradiction that Hashem passes through Egypt and kills all the firstborn at exactly midnight, since each one was killed exactly at the midnight of his specific area.
And to answer the second question, Moshe knew that if he told Pharaoh’s astrologers that Hashem would kill the firstborn exactly at midnight, and they would see that the firstborn were dying at “different” times, they would claim that Moshe was mistaken, since they would not know the exact time of midnight in each area. That is why Moshe told them kechatzot, around the time of chatzot.
On behalf of the Sheilot team, we wish you a Shabbos Shulem Umevoyroch.